Jonathan, Author at QUANTITATIVE RESEARCH AND TRADING

September 23, 2018September 23, 2018

High Frequency Trading with ADL – JonathanKinlay.com

Trading Technologies’ ADL is a visual programming language designed specifically for trading strategy development that is integrated in the company’s flagship XTrader product. Despite the radically different programming philosophy, my experience of working with ADL has been delightfully easy and strategies that would typically take many months of coding in C++ have been up and running in a matter of days or weeks. An extract of one such strategy, a high frequency scalping trade in the E-Mini S&P 500 futures, is shown in the graphic above. The interface and visual language is so intuitive to a trading system developer that even someone who has never seen ADL before can quickly grasp at least some of what it happening in the code.

Strategy Development in Low vs. High-Level Languages
What are the benefits of using a high level language like ADL compared to programming languages like C++/C# or Java that are traditionally used for trading system development? The chief advantage is speed of development: I would say that ADL offers the potential up the development process by at least one order of magnitude. A complex trading system would otherwise take months or even years to code and test in C++ or Java, can be implemented successfully and put into production in a matter of weeks in ADL. In this regard, the advantage of speed of development is one shared by many high level languages, including, for example, Matlab, R and Mathematica. But in ADL’s case the advantage in terms of time to implementation is aided by the fact that, unlike generalist tools such as MatLab, etc, ADL is designed specifically for trading system development. The ADL development environment comes equipped with compiled pre-built blocks designed to accomplish many of the common tasks associated with any trading system such as acquiring market data and handling orders. Even complex spread trades can be developed extremely quickly due to the very comprehensive library of pre-built blocks.

Integrating Research and Development
One of the drawbacks of using a higher level language for building trading systems is that, being interpreted rather than compiled, they are simply too slow – one or more orders of magnitude, typically – to be suitable for high frequency trading. I will come on to discuss the execution speed issue a little later. For now, let me bring up a second major advantage of ADL relative to other high level languages, as I see it. One of the issues that plagues trading system development is the difficulty of communication between researchers, who understand financial markets well, but systems architecture and design rather less so, and developers, whose skill set lies in design and programming, but whose knowledge of markets can often be sketchy. These difficulties are heightened where researchers might be using a high level language and relying on developers to re-code their prototype system to get it into production. Developers typically (and understandably) demand a high degree of specificity about the requirement and if it’s not included in the spec it won’t be in the final deliverable. Unfortunately, developing a successful trading system is a highly non-linear process and a researcher will typically have to iterate around the core idea repeatedly until they find a combination of alpha signal and entry/exit logic that works. In other words, researchers need flexibility, whereas developers require specificity. ADL helps address this issue by providing a development environment that is at once highly flexible and at the same time powerful enough to meet the demands of high frequency trading in a production environment. It means that, in theory, researchers and developers can speak a common language and use a common tool throughout the R&D development cycle. This is likely to reduce the kind of misunderstanding between researchers and developers that commonly arise (often setting back the implementation schedule significantly when they do).

Latency
Of course, at least some of the theoretical benefit of using ADL depends on execution speed. The way the problem is typically addressed with systems developed in high level languages like Matlab or R is to recode the entire system in something like C++, or to recode some of the most critical elements and plug those back into the main Matlab program as dlls. The latter approach works, and preserves the most important benefits of working in both high and low level languages, but the resulting system is likely to be sub-optimal and can be difficult to maintain. The approach taken by Trading Technologies with ADL is very different. Firstly, the component blocks are written in C# and in compiled form should run about as fast as native code. Secondly, systems written in ADL can be deployed immediately on a co-located algo server that is plugged directly into the exchange, thereby reducing latency to an acceptable level. While this is unlikely to sufficient for an ultra-high frequency system operating on the sub-millisecond level, it will probably suffice for high frequency systems that operate at speeds above above a few millisecs, trading up to say, around 100 times a day.

Fill Rate and Toxic Flow
For those not familiar with the HFT territory, let me provide an example of why the issues of execution speed and latency are so important. Below is a simulated performance record for a HFT system in ES futures. The system is designed to enter and exit using limit orders and trades around 120 times a day, with over 98% profitability, if we assume a 100% fill rate. So far so good. But a 100% fill rate is clearly unrealistic. Let’s look at a pessimistic scenario: what if we got filled on orders only when the limit price was exceeded? (For those familiar with the jargon, we are assuming a high level of flow toxicity) The outcome is rather different: Neither scenario is particularly realistic, but the outcome is much more likely to be closer to the second scenario rather than the first if we our execution speed is slow, or if we are using a retail platform such as Interactive Brokers or Tradestation, with long latency wait times. The reason is simple: our orders will always arrive late and join the limit order book at the back of the queue. In most cases the orders ahead of ours will exhaust demand at the specified limit price and the market will trade away without filling our order. At other times the market will fill our order whenever there is a large flow against us (i.e. a surge of sell orders into our limit buy), i.e. when there is significant toxic flow. The proposition is that, using ADL and the its high-speed trading infrastructure, we can hope to avoid the latter outcome. While we will never come close to achieving a 100% fill rate, we may come close enough to offset the inevitable losses from toxic flow and produce a decent return. Whether ADL is capable of fulfilling that potential remains to be seen.

More on ADL
For more information on ADL go here.

September 22, 2018

Equity Curve Money Management

Amongst a wide variety of money management methods that have evolved over the years, a perennial favorite is the use of the equity curve to guide position sizing. The most common version of this technique is to add to the existing position (whether long or short) depending on the relationship between the current value of the account equity (realized + unrealized PL) and its moving average. According to whether you believe that the equity curve is momentum driven, or mean reverting, you will add to your existing position when the equity move above (or, on the case of mean-reverting, below) the long term moving average.

In this article I want to discuss a slightly different version of equity curve money management, which is mean-reversion oriented. The underlying thesis is that your trading strategy has good profit characteristics, and while it suffers from the occasional, significant drawdown, it can be expected to recover from the downswings. You should therefore be looking to add to your positions when the equity curve moves down sufficiently, in the expectation that the trading strategy will recover. The extra contracts you add to your position during such downturns with increase the overall P&L. To illustrate the approach I am going to use a low frequency strategy on the S&P500 E-mini futures contract (ES). The performance of the strategy is summarized in the chart and table below.

(click to enlarge)

The overall results of the strategy are not bad: at over 87% the win rate is high as, too, is the profit factor of 2.72. And the strategy’s performance, although hardly stellar, has been quite consistent over the period from 1997. That said, most the profits derive from the long side, and the strategy suffers from the occasional large loss, including a significant drawdown of over 18% in 2000.

I am going to use this underlying strategy to illustrate how its performance can be improved with equity curve money management (ECMM). To start, we calculate a simple moving average of the equity curve, as before. However, in this variation of ECMM we then calculate offsets that are a number of standard deviations above or below the moving average. Typical default values for the moving average length might be 50 bars for a daily series, while we might use, say, +/- 2 S.D. above and below the moving average as our trigger levels. The idea is that we add to our position when the equity curve falls below the lower threshold level (moving average – 2x S.D) and then crosses back above it again. This is similar to how a trader might use Bollinger bands, or an oscillator like Stochastics. The chart below illustrates the procedure.

The lower and upper trigger levels are shown as green and yellow lines in the chart indicator (note that in this variant of ECMM we only use the lower level to add to positions).

After a significant drawdown early in October the equity curve begins to revert and crosses back over the lower threshold level on Oct 21. Applying our ECMM rule, we add to our existing long position the next day, Oct 22 (the same procedure would apply to adding to short positions). As you can see, our money management trade worked out very well, since the EC did continue to mean-revert as expected. We closed the trade on Nov 11, for a substantial, additional profit.

Now we have illustrated the procedure, let’s being to explore the potential of the ECMM idea in more detail. The first important point to understand is what ECMM will NOT do: i.e. reduce risk. Like all money management techniques that are designed to pyramid into positions, ECMM will INCREASE risk, leading to higher drawdowns. But ECMM should also increase profits: so the question is whether the potential for greater profits is sufficient to offset the risk of greater losses. If not, then there is a simpler alternative method of increasing profits: simply increase position size! It follows that one of the key metrics of performance to focus on in evaluating this technique is the ratio of PL to drawdown. Let’s look at some examples for our baseline strategy.

The chart shows the effect of adding a specified number of contracts to our existing long or short position whenever the equity curve crosses back above the lower trigger level, which in this case is set at 2xS.D below the 50-day moving average of the equity curve. As expected, the overall strategy P&L increases linearly in line with the number of additional contracts traded, from a base level of around $170,000, to over $500,000 when we trade an additional five contracts. So, too, does the profit factor rise from around 2.7 to around 5.0. That’s where the good news ends. Because, just as the strategy PL increases, so too does the size of the maximum drawdown, from $(18,500) in the baseline case to over $(83,000) when we trade an additional five contracts. In fact, the PL/Drawdown ratio declines from over 9.0 in the baseline case, to only 6.0 when we trade the ECMM strategy with five additional contracts. In terms of risk and reward, as measured by the PL/Drawdown ratio, we would be better off simply trading the baseline strategy: if we traded 3 contracts instead of 1 contract, then without any money management at all we would have made total profits of around $500,000, but with a drawdown of just over $(56,000). This is the same profit as produced with the 5-contract ECMM strategy, but with a drawdown that is $23,000 smaller.

How does this arise? Quite simply, our ECMM money management trades as not all automatic winners from the get-go (even if they eventually produce profits. In some cases, having crossed above the lower threshold level, the equity curve will subsequently cross back down below it again. As it does so, the additional contracts we have traded are now adding to the strategy drawdown.

This suggests that there might be a better alternative. How about if, instead of doing a single ECMM trade for, say, 5 additional contracts, we instead add an additional contract each time the equity curve crosses above the lower threshold level. Sure, we might give up some extra profits, but our drawdown should be lower, right? That turns out to be true. Unfortunately, however, profits are impacted more than the drawdown, so as a result the PL/Drawdown ratio shows the same precipitous decline:

Once again, we would be better off trading the baseline strategy in larger size, rather than using ECMM, even when we scale into the additional contracts.

What else can we try? An obvious trick to try is tweaking the threshold levels. We can do this by adjusting the # of standard deviations at which to set the trigger levels. Intuitively, it might seem that the obvious thing to do is set the threshold levels further apart, so that ECMM trades are triggered less frequently. But, as it turns out, this does not produce the desired effect. Instead, counter-intuitively, we have to set the threshold levels CLOSER to the moving average, at only +/-1x S.D. The results are shown in the chart below.

With these settings, the strategy PL and profit factor increase linearly, as before. So too does the strategy drawdown, but at a slower rate. As a consequence, the PL/Drawdown ration actually RISES, before declining at a moderate pace. Looking at the chart, it is apparent the optimal setting is trading two additional contracts with a threshold setting one standard deviation below the 50-day moving average of the equity curve.

Below are the overall results. With these settings the baseline strategy plus ECMM produces total profits of $334,000, a profit factor of 4.27 and a drawdown of $(35,212), making the PL/Drawdown ratio 9.50. Producing the same rate of profits using the baseline strategy alone would require us to trade two contracts, producing a slightly higher drawdown of almost $(37,000). So our ECMM strategy has increased overall profitability on a risk-adjusted basis.

(Click to enlarge)

CONCLUSION

It is certainly feasible to improve not only the overall profitability of a strategy using equity curve money management, but also the risk-adjusted performance. Whether ECMM will have much effect depends on the specifics of the underlying strategy, and the level at which the ECMM parameters are set to. These can be optimized on a walk-forward basis.

EASYLANGUAGE CODE

Inputs:

MALen(50),
SDMultiple(2),
PositionMult(1),
ExitAtBreakeven(False);

Var:
OpenEquity(0),
EquitySD(0),
EquityMA(0),
UpperEquityLevel(0),
LowerEquityLevel(0),
NShares(0);

OpenEquity=OpenPositionProfit+NetProfit;a
EquitySD=stddev(OpenEquity,MALen);
EquityMA=average(OpenEquity,MALen);
UpperEquityLevel=EquityMA + SDMultiple*EquitySD;
LowerEquityLevel=EquityMA-SDMultiple*EquitySD;
NShares=CurrentContracts*PositionMult;
If OpenEquity crosses above LowerEquityLevel then begin
If Marketposition > 0 then begin
Buy(“EnMark-LMM”) NShares shares next bar at market;
end;
If Marketposition < 0 then begin
Sell Short(“EnMark-SMM”) NShares shares next bar at market;
end;
end;
If ExitAtBreakeven then begin

If OpenEquity crosses above EquityMA then begin
If Marketposition > 1 then begin
Sell Short (“ExBE-LMM”) (Currentcontracts-1) shares next bar at market;
end;
If Marketposition < -1 then begin
Buy (“ExBE-SMM”) (Currentcontracts-1) shares next bar at market;
end;

end;
end;

September 21, 2018

Building Systematic Strategies – A New Approach

Anyone active in the quantitative space will tell you that it has become a great deal more competitive in recent years. Many quantitative trades and strategies are a lot more crowded than they used to be and returns from existing strategies are on the decline.

THE CHALLENGE

Meanwhile, costs have been steadily rising, as the technology arms race has accelerated, with more money being spent on hardware, communications and software than ever before. As lead times to develop new strategies have risen, the cost of acquiring and maintaining expensive development resources have spiraled upwards. It is getting harder to find new, profitable strategies, due in part to the over-grazing of existing methodologies and data sets (like the E-Mini futures, for example). There has, too, been a change in the direction of quantitative research in recent years. Where once it was simply a matter of acquiring the fastest pipe to as many relevant locations as possible, the marginal benefit of each extra $ spent on infrastructure has since fallen rapidly. New strategy research and development is now more model-driven than technology driven.

THE OPPORTUNITY

What is needed at this point is a new approach: one that accelerates the process of identifying new alpha signals, prototyping and testing new strategies and bringing them into production, leveraging existing battle-tested technologies and trading platforms.

GENETIC PROGRAMMING

Genetic programming, which has been around since the 1990’s when its use was pioneered in proteomics, enjoys significant advantages over traditional research and development methodologies.

GP is an evolutionary-based algorithmic methodology in which a system is given a set of simple rules, some data, and a fitness function that produces desired outcomes from combining the rules and applying them to the data. The idea is that, by testing large numbers of possible combinations of rules, typically in the millions, and allowing the most successful rules to propagate, eventually we will arrive at a strategy solution that offers the required characteristics.

ADVANTAGES OF GENETIC PROGRAMMING

The potential benefits of the GP approach are considerable: not only are strategies developed much more quickly and cost effectively (the price of some software and a single CPU vs. a small army of developers), the process is much more flexible. The inflexibility of the traditional approach to R&D is one of its principle shortcomings. The researcher produces a piece of research that is subsequently passed on to the development team. Developers are usually extremely rigid in their approach: when asked to deliver X, they will deliver X, not some variation on X. Unfortunately research is not an exact science: what looks good in a back-test environment may not pass muster when implemented in live trading. So researchers need to “iterate around” the idea, trying different combinations of entry and exit logic, for example, until they find a variant that works. Developers are lousy at this; GP systems excel at it.

CHALLENGES FOR THE GENETIC PROGRAMMING APPROACH

So enticing are the potential benefits of GP that it begs the question as to why the approach hasn’t been adopted more widely. One reason is the strong preference amongst researchers for an understandable – and testable – investment thesis. Researchers – and, more importantly, investors – are much more comfortable if they can articulate the premise behind a strategy. Even if a trade turns out to be a loser, we are generally more comfortable buying a stock on the supposition of, say, a positive outcome of a pending drug trial, than we are if required to trust the judgment of a black box, whose criteria are inherently unobservable.

Added to this, the GP approach suffers from three key drawbacks: data sufficiency, data mining and over-fitting. These are so well known that they hardly require further rehearsal. There have been many adverse outcomes resulting from poorly designed mechanical systems curve fitted to the data. Anyone who was active in the space in the 1990s will recall the hype over neural networks and the over-exaggerated claims made for their efficacy in trading system design. Genetic Programming, a far more general and powerful concept, suffered unfairly from the ensuing adverse publicity, although it does face many of the same challenges.

A NEW APPROACH

I began working in the field of genetic programming in the 1990’s, with my former colleague Haftan Eckholdt, at that time head of neuroscience at Yeshiva University, and we founded a hedge fund, Proteom Capital, based on that approach (large due to Haftan’s research). I and my colleagues at Systematic Strategies have continued to work on GP related ideas over the last twenty years, and during that period we have developed a methodology that address the weaknesses that have held back genetic programming from widespread adoption.

Firstly, we have evolved methods for transforming original data series that enables us to avoid over-using the same old data-sets and, more importantly, allows new patterns to be revealed in the underlying market structure. This effectively eliminates the data mining bias that has plagued the GP approach. At the same time, because our process produces a stronger signal relative to the background noise, we consume far less data – typically no more than a couple of years worth.

Secondly, we have found we can enhance the robustness of prototype strategies by using double-blind testing: i.e. data sets on which the performance of the model remains unknown to the machine, or the researcher, prior to the final model selection.

Finally, we are able to test not only the alpha signal, but also multiple variations of the trade expression, including different types of entry and exit logic, as well as profit targets and stop loss constraints.

OUTCOMES: ROBUST, PROFITABLE STRATEGIES

Taken together, these measures enable our GP system to produce strategies that not only have very high performance characteristics, but are also extremely robust. So, for example, having constructed a model using data only from the continuing bull market in equities in 2012 and 2013, the system is nonetheless capable of producing strategies that perform extremely well when tested out of sample over the highly volatility bear market conditions of 2008/09.

So stable are the results produced by many of the strategies, and so well risk-controlled, that it is possible to deploy leveraged money-managed techniques, such as Vince’s fixed fractional approach. Money management schemes take advantage of the high level of consistency in performance to increase the capital allocation to the strategy in a way that boosts returns without incurring a high risk of catastrophic loss. You can judge the benefits of applying these kinds of techniques in some of the strategies we have developed in equity, fixed income, commodity and energy futures which are described below.

CONCLUSION

After 20-30 years of incubation, the Genetic Programming approach to strategy research and development has come of age. It is now entirely feasible to develop trading systems that far outperform the overwhelming majority of strategies produced by human researchers, in a fraction of the time and for a fraction of the cost.

SAMPLE GP SYSTEMS

September 20, 2018September 20, 2018

Day Trading System in VIX Futures – JonathanKinlay.com

This is a follow up to my earlier post on a Calendar Spread Strategy in VIX Futures (more information on calendar spreads ).

The strategy trades the front two months in the CFE VIX futures contract, generating an annual profit of around $25,000 per spread.

DAY TRADING SYSTEM
I built an equivalent day trading system in VIX futures in Trading Technologies visual ADL language, using 1-min bar data for 2010, and tested the system out-of-sample in 2011-2014. (for more information on X-Trader/ ADL go here).

The annual net PL is around $20,000 per spread, with a win rate of 67%. On the downside, the profit factor is rather low and the average trade is barely 1/10 of a tick). Note that this is net of Bid-Ask spread of 0.05 ($50) and commission/transaction costs of $20 per round turn. These cost assumptions are reasonable for online trading at many brokerage firms.

However, the strategy requires you to work the spread to enter passively (thereby reducing the cost of entry). This is usually only feasible on a platform suitable for a high frequency trading, where you can assume that your orders have acceptable priority in the limit order queue. This will result in a reasonable proportion of your passive bids and offers will be executed. Typically the spread trade is held throughout the session, exiting on close (since this is a day trading system).

Overall, while the trading system characteristics are reasonable, the spread strategy is better suited to longer (i.e. overnight) holding periods, since the VIX futures market is not the most liquid and the tick value is large. We’ll take a look at other day trading strategies in more liquid products, like the S&P 500 e-mini futures, for example, in another post.

(click to enlarge)

September 19, 2018

A Calendar Spread Strategy in VIX Futures

I have been working on developing some high frequency spread strategies using Trading Technologies’ Algo Strategy Engine, which is extremely impressive (more on this in a later post). I decided to take a time out to experiment with a slower version of one of the trades, a calendar spread in VIX futures that trades the spread on the front two contracts. The strategy applies a variety of trend-following and mean-reversion indicators to trade the spread on a daily basis.

Modeling a spread strategy on a retail platform like Interactivebrokers or TradeStation is extremely challenging, due to the limitations of the platform and the Easylanguage programming language compared to professional platforms that are built for purpose, like TT’s XTrader and development tools like ADL. If you backtest strategies based on signals generated from the spread calculated using the last traded prices in the two securities, you will almost certainly see “phantom trades” – trades that could not be executed at the indicated spread price (for example, because both contracts last traded on the same side of the bid/ask spread). You also can’t easily simulate passive entry or exit strategies, which typically constrains you to using market orders for both legs, in and out of the spread. On the other hand, while using market orders would almost certainly be prohibitively expensive in a high frequency or daytrading context, in a low-frequency scenario the higher transaction costs entailed in aggressive entries and exits are typically amortized over far longer time frames.

In the following example I have allowed transaction costs of $100 per round turn and slippage of $0.1 (equivalent to $100) per spread. Daily settlement prices from Mar 2004 to June 2010 were used to fit the model, which was tested out of sample in the period July 2010 to June 2014. Results are summarized in the chart and table below.

Even burdened with significant transaction cost assumptions the strategy performance looks impressive on several counts, notably a profit factor in excess of 300, a win rate of over 90% and a Sortino Ratio of over 6. These features of the strategy prove robust (and even increase) during the four year out-of-sample period, although the annual net profit per spread declines to around $8,500, from $36,600 for the in-sample period. Even so, this being a straightforward calendar spread, it should be possible to trade the strategy in size at relative modest margin cost, making the strategy return highly attractive.

(click to enlarge)

September 18, 2018

What Wealth Managers and Family Offices Need to Understand About Alternative Investing

The most recent Morningstar survey provides an interesting snapshot of the state of the alternatives market. In 2013, for the third successive year, liquid alternatives was the fastest growing category of mutual funds, drawing in flows totaling $95.6 billion. The fastest growing subcategories have been long-short stock funds (growing more than 80% in 2013), nontraditional bond funds (79%) and “multi-alternative” fund-of-alts-funds products (57%).

Benchmarking Alternatives
The survey also provides some interesting insights into the misconceptions about alternative investments that remain prevalent amongst advisors, despite contrary indications provided by long-standing academic research. According to Morningstar, a significant proportion of advisors continue to use inappropriate benchmarks, such as the S&P 500 or Russell 2000, to evaluate alternatives funds (see Some advisers using ill-suited benchmarks to measure alts performance by Trevor Hunnicutt, Investment News July 2014). As Investment News points out, the problem with applying standards developed to measure the performance of funds that are designed to beat market benchmarks is that many alternative funds are intended to achieve other investment goals, such as reducing volatility or correlation. These funds will typically have under-performed standard equity indices during the bull market, causing investors to jettison them from their portfolios at a time when the additional protection they offer may be most needed.

This is but one example in a broader spectrum of issues about alternative investing that are poorly understood. Even where advisors recognize the need for a more appropriate hedge fund index to benchmark fund performance, several traps remain for the unwary. As shown in Brooks and Kat (The Statistical Properties of Hedge Fund Index Returns and Their Implications for Investors, Journal of Financial and Quantitative Analysis, 2001), there can be considerable heterogeneity between indices that aim to benchmark the same type of strategy, since indices tend to cover different parts of the alternatives universe. There are also significant differences between indices in terms of their survivorship bias – the tendency to overstate returns by ignoring poorly performing funds that have closed down (see Welcome to the Dark Side – Hedge Fund Attribution and Survivorship Bias, Amin and Kat, Working Paper, 2002). Hence, even amongst more savvy advisors, the perception of performance tends to be biased by the choice of index.

Risks and Benefits of Diversifying with Alternatives
An important and surprising discovery in relation to diversification with alternatives was revealed in Amin and Kat’s Diversification and Yield Enhancement with Hedge Funds (Working Paper, 2002). Their study showed that the median standard deviation of a portfolio of stocks, bonds and hedge funds reached its lowest point where the allocation to alternatives was 50%, far higher than the 1%-5% typically recommended by advisors.

Standard Deviation of Portfolios of Stocks, Bonds and 20 hedge Funds

Source: Diversification and Yield Enhancement with Hedge Funds, Amin and Kat, Working Paper, 2002

Another potential problem is that investors will not actually invest in the fund index that is used for benchmarking, but in a basket containing a much smaller number of funds, often through a fund of funds vehicle. The discrepancy in performance between benchmark and basket can often be substantial in the alternatives space.

Amin and Kat studied this problem in 2002 (Portfolios of Hedge Funds, Working Paper, 2002), by constructing hedge fund portfolios ranging in size from 1 to 20 funds and measuring their performance on a number of criteria that included, not just the average return and standard deviation, but also the skewness (a measure of the asymmetry of returns), kurtosis (a measure of the probability of extreme returns)and the correlation with the S&P 500 Index and the Salomon (now Citigroup) Government Bond Index. Their startling conclusion was that, in the alternatives space, diversification is not necessarily a good thing. As expected, as the number of funds in the basket is increased, the overall volatility drops substantially; but at the same time skewness drops and kurtosis and market correlation increase significantly. In other words, when adding more funds, the likelihood of a large loss increases and the diversification benefit declines. The researchers found that a good approximation to a typical hedge fund index could be constructed with a basket of just 15 well-chosen funds, in most cases.

Concerns about return distribution characteristics such as skewness and kurtosis may appear arcane, but these factors often become crucially important at just the wrong time, from the investor’s perspective. When things go wrong in the stock market they also tend to go wrong for hedge funds, as a fall in stock prices is typically accompanied by a drop in market liquidity, a widening of spreads and, often, an increase in stock loan costs. Equity market neutral and long/short funds that are typically long smaller cap stocks and short larger cap stocks will pay a higher price for the liquidity they need to maintain neutrality. Likewise, a market sell-off is likely to lead to postponing of M&A transactions that will have a negative impact on the performance of risk arbitrage funds. Nor are equity-related funds the only alternatives likely to suffer during a market sell-off. A market fall will typically be accompanied by widening credit spreads, which in turn will damage the performance of fixed income and convertible arbitrage funds. The key point is that, because they all share this risk, diversification among different funds will not do much to mitigate it.

Conclusions
Many advisors remain wedded to using traditional equity indices that are inappropriate benchmarks for alternative strategies. Even where more relevant indices are selected, they may suffer from survivorship and fund-selection bias.

In order to reap the diversification benefit from alternatives, research shows that investors should concentrate a significant proportion of their wealth in the limited number of alternatives funds, a portfolio strategy that is diametrically opposed to the “common sense” approach of many advisors.

Finally, advisors often overlook the latent correlation and liquidity risks inherent in alternatives that come into play during market down-turns, at precisely the time when investors are most dependent on diversification to mitigate market risk. Such risks can be managed, but only by paying attention to portfolio characteristics such as skewness and kurtosis, which alternative funds significantly impact.

September 17, 2018

Creating Robust, High-Performance Stock Portfolios

Summary

In this article, I am going to look at how stock portfolios should be constructed that best meet investment objectives.

The theoretical and practical difficulties of the widely adopted Modern Portfolio Theory approach limits its usefulness as a tool for portfolio construction.

MPT portfolios typically produce disappointing out-of-sample results, and will often underperform a naïve, equally-weighted stock portfolio.

The article introduces the concept of robust portfolio construction, which leads to portfolios that have more stable performance characteristics, including during periods of high volatility or market corrections.

The benefits of this approach include risk-adjusted returns that substantially exceed those of traditional portfolios, together with much lower drawdowns and correlations.

Market Timing

In an earlier article, I discussed how investors can enhance returns through the strategic use of market timing techniques to step out of the market during difficult conditions.

To emphasize the impact of market timing on investment returns, I have summarized in the chart below how a $1,000 investment would have grown over the 25-year period from July 1990 to June 2014. In the baseline scenario, we assume that the investment is made in a fund that tracks the S&P 500 Index and held for the full term. In the second scenario, we look at the outcome if the investor had stepped out of the market during the market downturns from March 2000 to Feb 2003 and from Jan 2007 to Feb 2009.

Fig. 1: Value of $1,000 Jul 1990-Jun 2014 – S&P 500 Index with and without Market Timing

Source: Yahoo Finance, 2014

After 25 years, the investment under the second scenario would have been worth approximately 5x as much as in the baseline scenario. Of course, perfect market timing is unlikely to be achievable. The best an investor can do is employ some kind of market timing indicator, such as the CBOE VIX index, as described in the previous article.

Equity Long Short

For those who mistrust the concept of market timing or who wish to remain invested in the market over the long term regardless of short-term market conditions, an alternative exists that bears consideration.

The equity long/short strategy, in which the investor buys certain stocks while shorting others, is a concept that reputedly originated with Alfred Jones in the 1940s. A long/short equity portfolio seeks to reduce overall market exposure, while profiting from stock gains in the long positions and price declines in the short positions. The idea is that the investor’s equity investments in the long positions are hedged to some degree against a general market decline by the offsetting short positions, from which the concept of a hedge fund is derived.

There are many variations on the long/short theme. Where the long and short positions are individually matched, the strategy is referred to as pairs trading. When the portfolio composition is structured in a way that the overall market exposure on the short side equates to that of the long side, leaving zero net market exposure, the strategy is typically referred to as market-neutral. Variations include dollar-neutral, where the dollar value of aggregate long and short positions is equalized, and beta-neutral, where the portfolio is structured in a way to yield a net zero overall market beta. But in the great majority of cases, such as, for example, in 130/30 strategies, there is a residual net long exposure to the market. Consequently, for the most part, long/short strategies are correlated with the overall market, but they will tend to outperform long-only strategies during market declines, while underperforming during strong market rallies.

Modern Portfolio Theory

Theories abound as to the best way to construct equity portfolios. The most commonly used approach is mean-variance optimization, a concept developed in the 1950s by Harry Markovitz (other more modern approaches include, for example, factor models or CVAR – conditional value at risk).

If we plot the risk and expected return of the assets under consideration, in what is referred to as the investment opportunity set, we see a characteristic “bullet” shape, the upper edge of which is called the efficient frontier (See Fig. 2). Assets on the efficient frontier produce the highest level of expected return for a given level of risk. Equivalently, a portfolio lying on the efficient frontier represents the combination offering the best possible expected return for a given risk level. It transpires that for efficient portfolios, the weights to be assigned to individual assets depend only on the volatilities of the individual assets and the correlation between them, and can be determined by simple linear programming. The inclusion of a riskless asset (such as US T-bills) allows us to construct the Capital Market Line, shown in the figure, which is tangent to the efficient frontier at the portfolio with the highest Sharpe Ratio, which is consequently referred to as the Tangency or Optimal Portfolio.

Fig. 2: Investment Opportunity Set and Efficient Frontier

Source: Wikipedia

Paradise Lost

Elegant as it is, MPT is open to challenge as a suitable basis for constructing investment portfolios. The Sharpe Ratio is often an inadequate representation of the investor’s utility function – for example, a strategy may have a high Sharpe Ratio but suffer from large drawdowns, behavior unlikely to be appealing to many investors. Of greater concern is the assumption of constant correlation between the assets in the investment universe. In fact, expected returns, volatilities and correlations fluctuate all the time, inducing changes in the shape of the efficient frontier and the composition of the optimal portfolio, which may be substantial. Not only is the composition of the optimal portfolio unstable, during times of financial crisis, all assets tend to become positively correlated and move down together. The supposed diversification benefit of MPT breaks down when it is needed the most.

I want to spend a little time on these critical issues before introducing a new methodology for portfolio construction. I will illustrate the procedure using a limited investment universe consisting of the dozen stocks listed below. This is, of course, a much more restricted universe than would typically apply in practice, but it does provide a span of different sectors and industries sufficient for our purpose.

Adobe Systems Inc. (NASDAQ:ADBE)

E. I. du Pont de Nemours and Company (NYSE:DD)

The Dow Chemical Company (NYSE:DOW)

Emerson Electric Co. (NYSE:EMR)

Honeywell International Inc. (NYSE:HON)

International Business Machines Corporation (NYSE:IBM)

McDonald’s Corp. (NYSE:MCD)

Oracle Corporation (NYSE:ORCL)

The Procter & Gamble Company (NYSE:PG)

Texas Instruments Inc. (NASDAQ:TXN)

Wells Fargo & Company (NYSE:WFC)

Williams Companies, Inc. (NYSE:WMB)

If we follow the procedure outlined in the preceding section, we arrive at the following depiction of the investment opportunity set and efficient frontier. Note that in the following, the S&P 500 index is used as a proxy for the market portfolio, while the equal portfolio designates a portfolio comprising identical dollar amounts invested in each stock.

Fig. 3: Investment Opportunity Set and Efficient Frontiers for the 12-Stock Portfolio

Source: MathWorks Inc.

As you can see, we have derived not one, but two, efficient frontiers. The first is the frontier for standard portfolios that are constrained to be long-only and without use of leverage. The second represents the frontier for 130/30 long-short portfolios, in which we permit leverage of 30%, so that long positions are overweight by a total of 30%, offset by a 30% short allocation. It turns out that in either case, the optimal portfolio yields an average annual return of around 13%, with annual volatility of around 17%, producing a Sharpe ratio of 0.75.

So far so good, but here, of course, we are estimating the optimal portfolio using the entire data set. In practice, we will need to estimate the optimal portfolio with available historical data and rebalance on a regular basis over time. Let’s assume that, starting in July 1995 and rolling forward month by month, we use the latest 60 months of available data to construct the efficient frontier and optimal portfolio.

Fig. 4 below illustrates the enormous variation in the shape of the efficient frontier over time, and in the risk/return profile of the optimal long-only portfolio, shown as the white line traversing the frontier surface.

Fig. 4: Time Evolution of the Efficient Frontier and Optimal Portfolio

Source: MathWorks Inc.

We see in Fig. 5 that the outcome of using the MPT approach is hardly very encouraging: the optimal long-only portfolio underperforms the market both in aggregate, over the entire back-test period, and consistently during the period from 2000-2011. The results for a 130/30 portfolio (not shown) are hardly an improvement, as the use of leverage, if anything, has a tendency to exacerbate portfolio turnover and other undesirable performance characteristics.

Fig. 5: Value of $1,000: Optimal Portfolio vs. S&P 500 Index, Jul 1995-Jun 2014

Source: MathWorks Inc.

Part of the reason for the poor performance of the optimal portfolio lies with the assumption of constant correlation. In fact, as illustrated in Fig 6, the average correlation between the monthly returns in the twelve stocks in our universe has fluctuated very substantially over the last twenty years, ranging from a low of just over 20% to a high in excess of 50%, with an annual volatility of 38%. Clearly, the assumption of constant correlation is unsafe.

Fig. 6: Average Correlation, Jul 1995-Jun 2014

Source: Yahoo Finance, 2014

To add to the difficulties, researchers have found that the out of sample performance of the naïve portfolio, in which equal dollar value is invested in each stock, is typically no worse than that of portfolios constructed using techniques such as mean-variance optimization or factor models¹. Due to the difficulty of accurately estimating asset correlations, it would require an estimation window of 3,000 months of historical data for a portfolio of only 25 assets to produce a mean-variance strategy that would outperform an equally-weighted portfolio!

Without piling on the agony with additional concerns about the MPT methodology, such as the assumption of Normality in asset returns, it is already clear that there are significant shortcomings to the approach.

Robust Portfolios

Many attempts have been made by its supporters to address the practical limitations of MPT, while other researchers have focused attention on alternative methodologies. In practice, however, it remains a challenge for any of the common techniques in use today to produce portfolios that will consistently outperform a naïve, equally-weighted portfolio. The approach discussed here represents a radical departure from standard methods, both in its objectives and in its methodology. I will discuss the general procedure without getting into all of the details, some of which are proprietary.

Let us revert for a moment to the initial discussion of market timing at the start of this article. We showed that if only we could time the market and step aside during major market declines, the outcome for the market portfolio would be a five-fold improvement in performance over the period from Aug 1990 to Jun 2014. In one sense, it would not take “much” to produce a substantial uplift in performance: what is needed is simply the ability to avoid the most extreme market drawdowns. We can identify this as a feature of what might be described as a “robust” portfolio, i.e. one with a limited tendency to participate in major market corrections. Focusing now on the general concept of “robustness”, what other characteristics might we want our ideal portfolio to have? We might consider, for example, some or all of the following:

Ratio of total returns to max drawdown
Percentage of profitable days
Number of drawdowns and average length of drawdowns
Sortino ratio
Correlation to perfect equity curve
Profit factor (ratio of gross profit to gross loss)
Variability in average correlation

The list is by no means exhaustive or prescriptive. But these factors relate to a common theme, which we may characterize as robustness. A portfolio or strategy constructed with these criteria in mind is likely to have a very different composition and set of performance characteristics when compared to an optimal portfolio in the mean-variance sense. Furthermore, it is by no means the case that the robustness of such a portfolio must come at the expense of lower expected returns. As we have seen, a portfolio which only produces a zero return during major market declines has far higher overall returns than one that is correlated with the market. If the portfolio can be constructed in a way that will tend to produce positive returns during market downturns, so much the better. In other words, what we are describing is a long/short portfolio whose correlation to the market adapts to market conditions, having a tendency to become negative when markets are in decline and positive when they are rising.

The first insight of this approach, then, is that we use different criteria, often multi-dimensional, to define optimality. These criteria have a tendency to produce portfolios that behave robustly, performing well during market declines or periods of high volatility, as well as during market rallies.

The second insight from the robust portfolio approach arises from the observation that, ideally, we would want to see much greater consistency in the correlations between assets in the investment universe than is typically the case for stock portfolios. Now, stock correlations are what they are and fluctuate as they will – there is not much one can do about that, at least directly. One solution might be to include other assets, such as commodities, into the mix, in an attempt to reduce and stabilize average asset correlations. But not only is this often undesirable, it is unnecessary – one can, in fact, reduce average correlation levels, while remaining entirely with the equity universe.

The solution to this apparent paradox is simple, albeit entirely at odds with the MPT approach. Instead of creating our portfolio on the basis of combining a group of stocks in some weighting scheme, we are first going to develop investment strategies for each of the stocks individually, before combining them into a portfolio. The strategies for each stock are designed according to several of the criteria of robustness we identified earlier. When combined together, these individual strategies will merge to become a portfolio, with allocations to each stock, just as in any other weighting scheme. And as with any other portfolio, we can set limits on allocations, turnover, or leverage. In this case, however, the resulting portfolio will, like its constituent strategies, display many of the desired characteristics of robustness.

Let’s take a look at how this works out for our sample universe of twelve stocks. I will begin by focusing on the results from the two critical periods from March 2000 to Feb 2003 and from Jan 2007 to Feb 2009.

Fig. 7: Robust Equity Long/Short vs. S&P 500 index, Mar 2000-Feb 2003

Source: Yahoo Finance, 2014

Fig. 8: Robust Equity Long/Short vs. S&P 500 index, Jan 2007-Feb 2009

Source: Yahoo Finance, 2014

As might be imagined, given its performance during these critical periods, the overall performance of the robust portfolio dominates the market portfolio over the entire period from 1990:

Fig. 9: Robust Equity Long/Short vs. S&P 500 index, Aug 1990-Jun 2014

Source: Yahoo Finance, 2014

It is worth pointing out that even during benign market conditions, such as those prevailing from, say, the end of 2012, the robust portfolio outperforms the market portfolio on a risk-adjusted basis: while the returns are comparable for both, around 36% in total, the annual volatility of the robust portfolio is only 4.8%, compared to 8.4% for the S&P 500 index.

A significant benefit to the robust portfolio derives from the much lower and more stable average correlation between its constituent strategies, compared to the average correlation between the individual equities, which we considered before. As can be seen from Fig. 10, average correlation levels remained under 10% for the robust portfolio, compared to around 25% for the mean-variance optimal portfolio until 2008, rising only to a maximum value of around 15% in 2009. Thereafter, average correlation levels have drifted consistently in the downward direction, and are now very close to zero. Overall, average correlations are much more stable for the constituents in the robust portfolio than for those in the traditional portfolio: annual volatility at 12.2% is less than one-third of the annual volatility of the latter, 38.1%.

Fig. 10: Average Correlations Robust Equity Long/Short vs. S&P 500 index, Aug 1990-Jun 2014

Source: Yahoo Finance, 2014

The much lower average correlation levels mean that it is possible to construct fully diversified portfolios in the robust portfolio framework with fewer assets than in the traditional MPT framework. Put another way, a robust portfolio with a small number of assets will typically produce higher returns with lower volatility than a traditional, optimal portfolio (in the MPT sense) constructed using the same underlying assets.

In terms of correlation of the portfolio itself, we find that over the period from Aug 1990 to June 2014, the robust portfolio exhibits close to zero net correlation with the market. However, the summary result disguises yet another important advantage of the robust portfolio. From the scatterplot shown in Fig. 11, we can see that, in fact, the robust portfolio has a tendency to adjust its correlation according to market conditions. When the market is moving positively, the robust portfolio tends to have a positive correlation, while during periods when the market is in decline, the robust portfolio tends to have a negative correlation.

Fig. 11: Correlation between Robust Equity Long/Short vs. S&P 500 index, Aug 1990-Jun 2014

Source: Yahoo Finance, 2014

Optimal Robust Portfolios

The robust portfolio referenced in our discussion hitherto is a naïve portfolio with equal dollar allocations to each individual equity strategy. What happens if we apply MPT to the equity strategy constituents and construct an “optimal” (in the mean-variance sense) robust portfolio?

The results from this procedure are summarized in Fig. 12, which shows the evolution of the efficient frontier, traversed by the risk/return path of the optimal robust portfolio. Both show considerable variability. In fact, however, both the frontier and optimal portfolio are far more stable than their equivalents for the traditional MPT strategy.

Fig. 12: Time Evolution of the Efficient Frontier and Optimal Robust Portfolio

Source: MathWorks Inc.

Fig. 13 compares the performance of the naïve robust portfolio and optimal robust portfolio. The optimal portfolio does demonstrate a small, material improvement in risk-adjusted returns, but at the cost of an increase in the maximum drawdown. It is an open question as to whether the modest improvement in performance is sufficient to justify the additional portfolio turnover and commensurate trading cost and operational risk. The incremental benefits are relatively minor, because the equally weighted portfolio is already well-diversified due to the low average correlation in its constituent strategies.

Fig. 13: Naïve vs. Optimal Robust Portfolio Performance Aug 1990-Jun 2014

Source: Yahoo Finance, 2014

Conclusion

The limitations of MPT in terms of its underlying assumptions and implementation challenges limits its usefulness as a practical tool for investors looking to construct equity portfolios that will enable them to achieve their investment objectives. Rather than seeking to optimize risk-adjusted returns in the traditional way, investors may be better served by identifying important characteristics of strategy robustness and using these to create strategies for individual equities that perform robustly across a wide range of market conditions. By constructing portfolios composed of such strategies, rather than using the underlying equities, investors may achieve higher, more stable returns under a broad range of market conditions, including periods of high volatility or market drawdown.

¹ Optimal Versus Naive Diversification: How Inefficient is the 1/N Portfolio Strategy?, Victor DeMiguel, Lorenzo Garlappi and Raman Uppal, The Review of Financial Studies, Vol. 22, Issue 5, 2007.

September 17, 2018September 18, 2018

Beating the S&P500 Index with a Low Convexity Portfolio

What is Beta Convexity?

Beta convexity is a measure of how stable a stock beta is across market regimes. The essential idea is to evaluate the beta of a stock during down-markets, separately from periods when the market is performing well. By choosing a portfolio of stocks with low beta-convexity we seek to stabilize the overall risk characteristics of our investment portfolio.

A primer on beta convexity and its applications is given in the following post:

In this post I am going to use the beta-convexity concept to construct a long-only equity portfolio capable of out-performing the benchmark S&P 500 index.

The post is in two parts. In the first section I outline the procedure in Mathematica for downloading data and creating a matrix of stock returns for the S&P 500 membership. This is purely about the mechanics, likely to be of interest chiefly to Mathematica users. The code deals with the issues of how to handle stocks with multiple different start dates and missing data, a problem that the analyst is faced with on a regular basis. Details are given in the pdf below. Let’s skip forward to the analysis.

Portfolio Formation & Rebalancing

We begin by importing the data saved using the data retrieval program, which comprises a matrix of (continuously compounded) monthly returns for the S&P500 Index and its constituent stocks. We select a portfolio size of 50 stocks, a test period of 20 years, with a formation period of 60 months and monthly rebalancing.

In the processing stage, for each month in our 20-year test period we calculate the beta convexity for each index constituent stock and select the 50 stocks that have the lowest beta-convexity during the prior 5-year formation period. We then compute the returns for an equally weighted basket of the chosen stocks over the following month. After that, we roll forward one month and repeat the exercise.

It turns out that beta-convexity tends to be quite unstable, as illustrated for a small sample of component stocks in the chart below:

A snapshot of estimated convexity factors is shown in the following table. As you can see, there is considerable cross-sectional dispersion in convexity, in addition to time-series dependency.

At any point in time the cross-sectional dispersion is well described by a Weibull distribution, which passes all of the usual goodness-of-fit tests.

Performance Results

We compare the annual returns and standard deviation of the low convexity portfolio with the S&P500 benchmark in the table below. The results indicate that the average gross annual return of a low-convexity portfolio of 50 stocks is more than double that of the benchmark, with a comparable level of volatility. The portfolio also has slightly higher skewness and kurtosis than the benchmark, both desirable characteristics.

Portfolio Alpha & Beta Estimation

Using the standard linear CAPM model we estimate the annual alpha of the low-convexity portfolio to be around 7.39%, with a beta of 0.89.

Beta Convexity of the Low Convexity Portfolio

As we might anticipate, the beta convexity of the portfolio is very low since it comprises stocks with the lowest beta-convexity:

Conclusion: Beating the Benchmark S&P500 Index

Using a beta-convexity factor model, we are able to construct a small portfolio that matches the benchmark index in terms of volatility, but with markedly superior annual returns. Larger portfolios offering greater liquidity produce slightly lower alpha, but a 100-200 stock portfolio typically produce at least double the annual rate of return of the benchmark over the 20-year test period.

For those interested, we shall shortly be offering a low-convexity strategy on our Systematic Algotrading platform – see details below:

Section on Data Retrieval and Processing

Data Retrieval

September 16, 2018

Pattern Trading

Summary

Pattern trading rules try to identify profit opportunities, based on short term price patterns.
An exhaustive test of simple pattern trading rules was conducted for several stocks, incorporating forecasts of the Open, High, Low and Close prices.
There is clear evidence that pattern trading rules continue to work consistently for many stocks.
Almost all of the optimal pattern trading rules suggest buying the stock if the close is below the mid-range of the day.
This “buy the dips” approach can sometimes be improved by overlaying additional conditions, or signals from forecasting models.

Trading Pattern Rules

From time to time one comes across examples of trading pattern rules that appear to work. By “pattern rule”, I mean something along the lines of: “if the stock closes below the open and today’s high is greater than yesterday’s high, then buy tomorrow’s open”.

Trading rules of this kind are typically one-of-a-kind oddities that only work for limited periods, or specific securities. But I was curious enough to want to investigate the concept of pattern trading, to see if there might be some patterns that are generally applicable and potentially worth trading.

To my surprise, I was able to find such a rule, which I will elaborate on in this article. The rule appears to work consistently for a wide range of stocks, across long time frames. While perhaps not interesting enough to trade by itself, the rule might provide some useful insight and, possibly, be combined with other indicators in a more elaborate trading strategy.

The original basis for this piece of research was the idea of using vector autoregression models to forecast the daily O/H/L/C prices of a stock. The underlying thesis is that there might be information in the historical values of these variables that, combined together, could produce more useful forecasts than, say, using close prices alone. In technical terms, we say that the O/H/L/C price series are cointegrated, which one might think of as a more robust kind of correlation: cointegrated series tend to continue to move together for some underlying economic reason, whereas series that are merely correlated will often see that purely statistical relationship break down. In this case the economic relationship between the O/H/L/C series is clear: the high price will always be greater than the low price, and the open and close prices will always lie between the two. Furthermore, the prices cannot drift arbitrarily far apart indefinitely, since volatility is finite and mean-reverting. So there is some kind of rationale for using a vector autoregression model in this context. But I don’t want to dwell on this idea too much, as it turns out to be useful only at the margin.

To keep it simple I decided to focus attention on simple pattern trades of the following kind:

If Rule1 and/or Rule2 then Trade

Rule1 and Rule2 are simple logical statements of the kind: “Today’s Open greater than yesterday’s Close”, or “today’s High below yesterday’s Low”. The trade can be expressed in combinations of the form “Buy today’s Open, Sell today’s Close”, or “Buy today’s Close, Sell tomorrow’s Close”.

In my model I had to consider rules combining not only the O/H/L/C prices from yesterday, today and tomorrow, but also forecast O/H/L/C prices from the vector autoregression model. This gave rise to hundreds of thousands of possibilities. A brute-force test of every one of them would certainly be feasible, but rather tedious to execute. And many of the possible rules would be redundant – for example a rule such as : “if today’s open is lower than today’s close, buy today’s open”. Rules of that kind will certainly make a great deal of money, but they aren’t practical, unfortunately!

To keep the number of possibilities to a workable number, I restricted the trading rule to the following: “Buy today’s close, sell tomorrow’s close”. Consequently, we are considering long-only trading strategies and we ignore any rules that might require us to short a stock.

I chose stocks with long histories, dating back to at least the beginning of the 1970’s, in order to provide sufficient data to construct the VAR model. Data from the period from Jan 1970 to Dec 2012 were used to estimate the model, and the performance of the various possible trading rules was evaluated using out-of-sample data from Jan 2013 to Jun 2014.

For ease of illustration the algorithms were coded up in MS-Excel (a copy of the Excel workbook is available on request). In evaluating trading rule performance an allowance was made of $1c per share in commission and $2c per share in slippage. Position size was fixed at 1,000 shares. Considering that the trading rules requires entry and exit at market close, a greater allowance for slippage may be required for some stocks. In addition, we should note the practical difficulties of trading a sizeable position at the close, especially in situations where the stock price may be very near to key levels such as the intra-day high or low that our trading rule might want to take account of.

As a further caveat, we should note that there is an element of survivor bias here: in order to fit this test protocol, stocks would have had to survive from the 1970’s to the present day. Many stocks that were current at the start of that period are no longer in existence, due to mergers, bankruptcies, etc. Excluding such stocks from the evaluation will tend to inflate the test results. It should be said that I did conduct similar tests on several now-defunct stocks, for which the outcomes were similar to those presented here, but a fully survivor-bias corrected study is beyond the scope of this article. With that caveat behind us, let’s take a look at some of the results.

Trading Pattern Analysis

Fig. 1 below shows the summary output from the test for the 3M Company (NYSE:MMM). At the top you can see the best trading rule that the system was able to find for this particular stock. In simple English, the rule tells you to buy today’s close in MMM and sell tomorrow’s close, if the stock opened below the forecast of yesterday’s high price and, in addition, the stock closed below the midrange of the day (the average of today’s high and low prices).

Fig. 1 Summary Analysis for MMM

Source: Yahoo Finance.

The in-sample results from Jan 2000, summarized in left-hand table in Fig. 2 below, are hardly stellar, but do show evidence of a small, but significant edge, with total net returns of 165%, profit factor of 1.38 and % win rate of 54%. And while the trading rule is, ultimately, outperformed by a simple buy-and-hold strategy, after taking into account transaction costs, for extended periods (e.g. 2009-2012), investors would have been better off had they used the trading rule, because it successfully avoided the worst of the effects of the 2008/09 market crash.

Out-of-sample results, shown in the right-hand table, are less encouraging, but net returns are nonetheless positive and the % win rate actually increases to 55%.

Fig 2. Trade Rule Performance

Source: Yahoo Finance.

I noted earlier that the first part of our trading rule for MMM involved comparing the opening price to the forecast of yesterday’s high, produced by the vector autoregression model, while the second part of the trading rule references only the midrange and closing prices. How much added value does the VAR model provide? We can test this by eliminating the first part of the rule and considering all days in which the stock closed below the midrange. The results turn out to as shown in Fig. 3.

Fig. 3 Performance of Simplified Trading Rule

Source: Yahoo Finance.

As expected, the in-sample results from our shortened trading rule are certainly inferior to the original rule, in which the VAR model forecasts played a role. But the out-of-sample performance of the simplified rule is actually improved – not only is the net return higher than before, so too is the % win rate, by a couple of percentage points.

A similar pattern emerges for many other stocks: in almost every case, our test algorithm finds that the best trading rule buys the close, based on a comparison of the closing price to the mid-range price. In some cases, the in-sample test results are improved by adding further conditions, such as we saw in the case of MMM. But, as with MMM, we often find that the additional benefit derived from use of the autoregression model forecasts fails to improve trading rule results in the out-of-sample period, and indeed often makes them worse.

Conclusion

In general, we find evidence that a simple trading rule based on a comparison of the closing price to the mid-range price appears to work for many stocks, across long time spans.

In a sense, this simple trading rule is already well known: it is just a variant of the “buy the dips” idea, where, in this case, we define a dip as being when the stock closes below the mid-range of the day, rather than, say, below a moving average level. The economic basis for this finding is also well known: stocks have positive drift. But it is interesting to find yet another confirmation of this well-known idea. And it leaves open the possibility that the trading concept could be further improved by introducing additional rules, trading indicators, and model forecasts to the mix.

September 14, 2018

More on Strategy Robustness

Commentators have made the point that a high % win rate is not enough.

Yes, you obviously want to pay attention to other performance metrics also, such as profit factor. In fact, there is no reason why you shouldn’t consider an objective function that explicitly combines various desirable performance measures, for example:

net profit * % win rate * profit factor

Another approach is to build the model using a data set spanning a different period. I did this with WFC using data from 1990, rather than 1970. Not only was the performance from 1990-2014 better, so too was the performance during the OOS period 1970-1989. Profit factor was 2.49 and %Win rate was 70% across the 44 year period from 1970. For the period from 1990, the performance metrics increase to 3.04 and 73%, respectively.

So in this case, it appears, a most robust strategy resulted from using less data, rather than more. At first this appears counterintuitive. But it’s quite possible for a strategy to be over-condition on behavior that is no longer relevant to the market today. Eliminating such conditioning can sometimes enable strategies to emerge that have greater longevity.