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Mean Reversion Strategy: All You Need to Know

Godfrey Peay

Feb 16, 2022 15:35

Mean reversion is a financial theory which recommends that, after a severe rate relocation, asset rates tend to return back to typical or typical levels. Costs consistently oscillate around the mean or average rate but tend to return to that same average rate over and over.


Mean reversion does not just apply to property costs. It can be likewise applied to volatility, incomes, revenues development rates and technical sign levels. Keep reading to discover how to compute the mean reversion formula and how to apply mean reversion strategies when trading within the financial markets.


This post contains an in-depth guide for creating a mean reversion trading strategy.


You will learn what mean reversion is, how to trade it, 10 actions for developing a system and a complete example of a mean reversion system and all you require to understand about mean reversion strategy.

What Is Mean Reversion

Mean reversion, or reversion to the mean, is a theory utilized in finance that suggests that property price volatility and historical returns ultimately will revert to the long-run mean or average level of the entire dataset. This mean level can appear in a number of contexts such as financial growth, the volatility of a stock, a stock's price-to-earnings ratio (P/E ratio), or the average return of an industry. The idea of mean reversion is rooted in a well known principle called regression to the mean.


Mean reversion in trading thinks that extreme cost moves are hard to sustain for extended durations. Traders who take part in mean reversion trading have actually developed lots of methods for capitalising on the theory. In all cases, they are wagering that a severe level-- whether it be volatility, price, development, or a technical indication-- will return to the average.


Markets are permanently moving in and out of stages of mean reversion and momentum. Therefore it's possible to develop methods for both types of market.


A simplified example of a mean reversion strategy is to buy a stock after it has had a large fall in price. When a stock has actually seen a huge drop, there's usually a good chance that it will get better to a more typical level.


Simply put, things tend to level gradually.


For instance:

  • If a soccer group scores an unusual amount of objectives in a match, the next game they will most likely scorer closer to their average.

  • If the first individual you see today is uncommonly tall, the next person you see will most likely be much shorter.

  • If the Dow Jones Industrial Average drops 20% this month, it will most likely fall less than that next month.


The method to use this strategy in the market is to look for severe events and after that wager that things will revert back to nearer the average.


However, you'll discover that lots of mean reversion traders don't in fact believe that any historical mean holds significance.


Instead, lots of see them as hassle-free referral points. If a stock is 3 standard deviations away from its 10-day mean, that's an indicator that it just made a large upside relocation. And there are possibly successful signals to be gleaned from that.


As a generality, stocks, and indices in particular, have a strong tendency to indicate revert, rather than products and currencies, which tend to trend more.


However why is this?


The scholastic literature raises lots of prospective explanations, however I think utilize and margin make the most sense.


When trading stocks, the margin requirements are high.


You generally need to commit at least 25% in margin to the position, making stock trading systems capital intensive.


Compare this to the futures markets, where maintenance margin requirements are routinely less than 10% of the contract's notional worth. Likewise, substantial leverage is offered in the forex markets.


So why is this considerable?


When your stock positions are cash-secured, your direct exposure levels to specific positions increase considerably when those positions grow in value.


This necessitates rebalancing, which creates selling pressure in the best-performing stocks as they continue to surpass.


Contrast this to product and currencies, where even highly leveraged portfolios only use a portion of their total cash. It ends up being easier to comprehend why there's less friction to the occurrence of patterns in these markets.


Mean reversion strategies fade large discrepancies from historical rates. Buying stocks at 52-week lows is a simple example, while a statistical arbitrage pairs-trading system is more intricate.


The 52-week low strategy presumes that the stocks have actually been sold indiscriminately and are due for a bounce back to some historic mean. The concept here is that the stocks have just gone down too much.


A pairs-trading strategy, whether it's based on the relationship in between two similar companies, or perhaps in between two shares classes of the exact same stock, assumes that you can successfully trade when there's a substantial variance from the historic correlation.

Key Takeaways

  • Mean reversion, in financing, recommends that different phenomena of interest such as asset prices and volatility of returns eventually go back to their long-term typical levels.

  • The mean reversion theory has resulted in many investment techniques, from stock trading methods to alternatives rates models.

  • Mean reversion trading attempts to take advantage of severe changes in the rate of a specific security, assuming that it will go back to its previous state.

The Basics of Mean Reversion 

Reversion to the mean involves backtracking a condition back to its long-run typical state. The principle presumes that a level that wanders off far from the long-lasting standard or pattern will again return, reverting to its understood state or nonreligious pattern.


This theory has actually led to numerous investing strategies that include the purchase or sale of stocks or other securities whose recent performances have differed greatly from their historic averages. Nevertheless, a modification in returns likewise could be an indication that a company no longer has the exact same potential customers it when did, in which case it is less likely that mean reversion would happen.


Percentage returns and prices are not the only procedures considered in mean reverting; rates of interest or even the P/E ratio of a company can be based on this phenomenon.    

Mean reversion formula

To understand and compute mean reversion, traders require to calculate the mean. The mean is the typical price over an offered number of data points.


On a property's trading chart, the mean is easily represented by a basic moving average (SMA). The SMA determines the typical cost in the cost series. Over time, costs tend to oscillate around the average or SMA, ultimately returning to it.


Trades can use different metrics, such as distance from the SMA, to help to establish when the cost might revert back to the mean. Technical signs such as Bollinger Bands ®, regression channels, Keltner channels, and Envelopes each have their own formula and attempt to inform traders when the price is near severe levels and might go back. Nevertheless, as constantly in trading, these can only supply signals and are not a clear indicator of reversal.


The following chart reveals the Euro 50 stock index oscillating around the 50-week easy moving average over a five-year duration. The same idea applies to much shorter timeframes.



Example of mean reversion 

While an instrument's price tends to revert to the average gradually, this does not constantly indicate that the cost will hang back to the mean, or that the rate will rise to suggest. The mean is likewise moving, so if the cost stalls and doesn't move much, the mean cost has time to catch up. That too counts as mean reversion.


The following EUR/USD chart shows a year's worth of daily candlesticks. At times, the price oscillates around the mean. At other times, the cost accelerates far from the mean. The mean (SMA) follows and the two eventually cross paths again.



Mean Reversion Strategies

Mean reversion strategies try to record profits as the rate of a property go back to more normal levels, or the average. When considering utilizing a mean reversion strategy in your trading, remember that a cost increasing far from the mean doesn't necessarily show that the price will fall. The mean might also simply move up to meet the rate. That would also constitute reversion to the mean due to the fact that the rate is back in line with its average. While reversion to the mean occurs regularly, prices seldom stay precisely at the mean for long. Below are some popular examples of mean reversion strategies.

Different Ways To Trade Mean Reversion 

A basic mean reversion strategy would be to purchase a stock after an abnormally big drop in cost wagering that the stock rebounds to a more regular level.


However, there are numerous other manner ins which financiers and traders apply the theory of mean reversion.

Technical Indicators

Technical indicators like RSI can be used to discover severe oversold or overbought price levels. These can act as good levels to enter and exit mean reversion trades.


Standard deviation, Bollinger Bands, Money Flow, range from a moving average, can all be utilized to locate extreme or uncommon price moves. An excellent mean reversion sign determines extremes in rates that are most likely to be short-term, not irreversible.

Financial Information/ Fundamentals

Some financiers will look at monetary info such as PE ratios or revenues reports.


If a company reports strong quarterly earnings way above its long term average, the next quarter it will probably report closer to its average.


There are numerous factors at play which can add to extreme outcomes. Many of which struggle with natural mean reversion. For instance, the weather.


Similarly, if a stock has an uncommonly low PE ratio, a financier may buy the stock betting that the business is undervalued and the PE will go back to a more typical level.

Economic Indicators

Some financiers will look for mean reversion in economic indicators.


For example unemployment, GDP or Shiller's CAPE (cyclically changed price to earnings).


When Shiller's CAPE (listed below) is above average it suggests that stocks are traditionally expensive. Lots of investors trim their direct exposure to the stock exchange as a result.

Sentiment Indicators

Since the marketplace is a reflection of the crowd, some investors will look at sentiment indicators like investor confidence. Mean reversion signs like these frequently find good turning points.


For instance, if 70% of financiers are bearish, that might be a signal of too much pessimism in the market.


Historically, financier studies have actually shown financiers become more cynical near market lows and more confident near market peaks.


The chart below is the AAII Investor Sentiment Index and it shows clear mean reversion qualities. It is outlined against the S&P 500 Index (blue):




There are peaks in investor belief near market highs such as in January 2000. There are also troughs near market bottoms such as March 2009 and May 2016.

Pairs Trading

Pairs trading includes discovering two extremely correlated possessions. The costs of these possessions tend to move together. When the costs differ one another; for instance, one drops when the other doesn't; this produces a prospective mean reversion trade. This is also sometimes referred to as statistical arbitrage.


For example, the EUR/USD and GBP/USD frequently relocate the exact same instructions. Yet on the far right of the listed below EUR/USD chart, the GBP/USD is increasing (red line) while the EUR/USD (candles) is falling. If history is any sign, then those who pairs ought to ultimately begin relocating the very same direction again.




A trader might possibly purchase the underperforming set and brief the stronger set. This produces the chance to benefit if the pairs begin to line up again. A pairs trade requires buying and selling at the same time. It does not matter to a pairs trader which asset increases or falls; they are simply wagering that the two rates will assemble back to each other and start moving in alignment once again.


Given that it is possible that the two possessions may stagnate in unison again, a stop-loss can be utilized to control the possible loss on each trade. The earnings capacity if the properties return towards each other need to be ample to offset deal expenses, otherwise the trade might be disregarded. Tiny divergences between correlated possessions are frequently not considered to be worth trading.


Because a sets trade includes buying one asset and offering another, you might think about the hedge ratio, which is identified by just how much one asset relocations relative to the other. If one property relocations 1% daily and the other asset moves 2% daily, the position in the 2% asset must be half of the 1% asset. This is due to the fact that if a possession moves more, we don't need as much of that position to earn a profit when compared to a property that is moving less.

Directional vs. Relationship Mean Reversion. 

Mean reversion is a catch-all for various techniques that all share the typical quality of fading variances from a historical mean.


That mean is regularly cost, however it can likewise be a measure of appraisal or comparable fundamental signs. 

Directional Mean Reversion

Directional mean reversion strategies involve forecasting a directional price move in a particular security.


For example, if Apple stock falls 2 standard deviations from it's 90-day linear regression, we may anticipate the net returns in those scenarios to lean favorable.


There's several methods to create a mean reversion system, whether it's consecutive closes, a variance from an average, or an indicator value. All of them basically boil down to "buy when a stock drops excessive" or "sell when a stock has actually increased too much.".

Relationship Mean Reversion

The majority of professional mean reversion traders do not trade directionally. Rather, they trade the relationships in between securities. An easy example is statistical arbitrage between two share classes.


For the most part, both shares have nearly identical intrinsic value and ought to be trading at the same worth.


When dislocations in these share costs happen, pairs-traders will buy the cheaper share and offer the more costly share, betting that the delta in between the two will tighten up.

Intraday Mean Reversion Trading Strategy

Intraday methods involve buying and selling several properties throughout a single day and positions are usually not held overnight. With day trading, some traders decide to take trades around a moving average.


If there is an uptrend, the rate tends to go up from the average and then fall back to it. When the cost comes back to the average, this might provide a purchasing opportunity. If there is a sag, then the rate tends to fall below the average and then rally back to it. When the rate is near to the average, this may present an opportunity to take a short position (sell) rather.


An intraday mean reversion strategy works best when a strong trend is present, combined with a moving average where the rate tends to come up to it and then relocates the trending instructions. It does not work too when a strong trend is not present. Trading in the same direction as a strong trend is typically described as a momentum trading.

Arguments Against Mean Reversion

Up until now we have looked at some ways financiers approach mean reversion and how it's grounded in a concept called regression to the mean.


Nevertheless, mean reversion as applied to financial markets, does have its critics.

Markets Are Efficient Criticism

Supporters of effective market theories believe that markets reflect all available info.


It is therefore not possible to beat the market with a mean reversion algorithm (or any other technique) without some kind of details or illegal benefit.


In other words, if a stock falls 20% in a day, there is a justified factor for that drop.


The stock has actually been up to cost in the current info and there is no reason that the stock must recuperate even if it had a big fall.


There is some reality to the efficient markets hypothesis. If you analyze stock rates in detail you'll find they frequently show homes of a random walk.


However, efficient market hypothesis likewise has significant defects. You only need to see the crazy moves in shares like GameStop and AMC to understand that markets are not efficient all of the time.


This imbalance is what allows mean reversion trading methods to grow.


Who wants to live in a world where you can not reasonably generate income on a stock since the marketplaces are completely efficient? There will always be a time when you have an edge over the market. This theory just does not hold up.

Poor Performance Criticism

There is likewise criticism surrounding the efficiency of mean reversion indicators such as Shiller's CAPE.


CAPE has a good record of market timing over the last 100 years which is why it has ended up being such a popular tool.


But closer examination exposes that the majority of the gains can be found in the first very first 50 years. In the most recent 50 years, the ratio has actually done even worse than buy and hold.


There is an argument that some mean reversion indications like CAPE are based upon insufficient sample sizes.


A hundred or two a century might sound like enough time however if only a few signals are created, the sample size may still be too little to make a solid judgement.

Illogical Strategy Criticism 

One flaw with a mean reversion strategy is that in theory, the more a stock falls, the much better the setup becomes. This can trigger problems with danger management.


For example, picture you buy a stock after a 10% fall.


Instead of the stock rebounding, it goes on to fall another 10% the next day.


Despite the fact that you are losing cash, a mean reversion strategy will likely see the drop as another buy signal.


Mean reversion needs you to hold on to your loser and even increase your position in this scenario.


From a danger management point of view it can make more sense to cut your losses at this moment. However this breaks the idea of mean reversion. This leads to a sensible disparity.


If you keep increasing your position in a stock that doesn't rebound you will eventually explode.


In reality, however, effective mean reversion traders understand everything about this concern and have actually developed easy guidelines to overcome it.


For example, they will utilize time based exits, repaired stop losses or strategies to scale in to trades slowly.

Limitations of Mean Reversion

The return to a typical pattern is not guaranteed, as unexpected highs or lows could suggest a shift in the standard. Such occasions might include, however are not restricted to, brand-new product releases or developments on the positive side, or remembers and claims on the unfavorable side.


An asset could experience a mean reversion even in the most extreme occasion. But similar to most market activity, there are few warranties about how particular occasions will or will not affect the general appeal of specific securities.

Building a Mean Reversion Trading Strategy Step by Step

Now we have talked about some background, I am going to detail more about my procedure for developing mean reversion trading systems. I think we can break this procedure down into approximately 10 steps. All of it begins with preparing yourself the right tools for the job.

Step 1: Software

An important part of constructing a trading method is to have a method to backtest your method on historical information. Backtesting does not guarantee that you will find a profitable strategy however it is the very best tool we have for finding methods that work.


The primary step is to acquire a great backtesting platform and find out how to utilize it.

Step 2: Data

The next action is to get hold of some good quality data with which to backtest your techniques. If you don't have excellent information, then any analysis you do is going to be flawed.

Step 3: Have a Plan 

When you have actually arranged your backtest environment, it's time to make some decisions about what you wish to test and what you hope to get out of your testing.

Step 4: Buy and Sell Rules

For a mean reversion strategy to work, you wish to discover severe occasions that have a high opportunity of seeing a reversal.

Step 5: Initial Testing

Once you have some basic trading rules establish you require to get these configured into code so that you can do some initial screening on a little window of in-sample data.


You must beware not to use up too much data because you want to be able to run some more sophisticated tests later on.


At this moment you are just running some crude tests to see if your idea has any merit. This is before you add any other expensive rules or position sizing.

Step 6: Position Sizing for Mean Reversion Trading

If your mean going back method passes initial testing, you can begin to take it more seriously and include components that will help it change into a more powerful model.

Step 7: Adding More Rules

When you have your buy and sell guidelines sorted you will probably wish to include some extra rules to enhance the performance and logic of the system.

Step 8: Optimisations and Walk Forward Analysis

The more you advance through the steps and the more rules you contribute to your trading system the more issue you need to pay versus the risks of curve fitting and choice bias.

Step 9: Stress Testing and Evaluation

When you run a backtest, depending upon your software application platform, you will be revealed a number of metrics, statistics and charts with which to assess your system.

Step 10: Live Trading And Feedback

The last action when building your mean reversion trading strategy is to have actually a process established for taking your system live and after that tracking its development.

Mean Reversion Strategy Summerized 

Mean reversion trading is emotionally difficult. Mean reversion is an useful market concept to understand, but it does not ensure successful trading. While costs do tend to go back to the mean gradually, we can't understand for sure, ahead of time, when that will happen. Prices can continue moving far from the mean for longer than expected. Also, pattern instructions may alter, or just how much or how little the cost moves may change. Just because a price has actually risen doesn't mean it will be up to the mean; the mean might also rise to meet the cost.


Because of these unknowns, most expert traders have rigorous risk-management protocols. They can specify an exit point where their position will close out if the cost doesn't move in their expected instructions, helping to reduce losses as much as possible.


Nevertheless, mean reversion trading can be highly gratifying exactly due to the fact that it's difficult and a less "crowded trade."