What Is Mean Reversion, and How Do Investors Use It?


Mean reversion is a key concept in finance, suggesting that asset prices and returns tend to revert to their long-term average levels over time. In this article, we explore the basics of mean reversion, its applications in investment strategies, and its limitations. Discover how investors use mean reversion to make informed decisions in the world of finance.


Mean reversion, or reversion to the mean, is a fundamental theory in finance that plays a crucial role in shaping investment strategies. This theory suggests that asset prices and historical returns have a tendency to revert to the long-run mean or average level of the entire dataset. While this concept may seem abstract, its applications are far-reaching and valuable for investors.

The Basics of Mean Reversion

Mean reversion involves the idea of retracing a condition back to its long-run average state. The fundamental assumption is that any level that strays significantly from the long-term norm or trend will eventually return, reverting to its understood state or secular trend.

This theory has given rise to numerous investing strategies involving the purchase or sale of stocks or other securities whose recent performances have deviated greatly from their historical averages. However, it’s essential to note that a change in returns could also signal a shift in a company’s prospects, in which case mean reversion becomes less likely.

Mean reversion isn’t limited to just percentage returns and prices. Factors such as interest rates or a company’s price-to-earnings (P/E) ratio can also be subject to this phenomenon. However, it primarily focuses on the reversion of relatively extreme changes, as normal growth and fluctuations are expected in any market.

Using the Mean Reversion Theory

The mean reversion theory is a valuable tool in statistical analysis of market conditions and can form the basis of an overall trading strategy. It aligns perfectly with the age-old investment adage of “buying low and selling high” by seeking out abnormal activity that is likely to revert to a more typical pattern.

Additionally, mean reversion has found applications in options pricing, where it describes the observation that an asset’s volatility tends to fluctuate around a long-term average. Many options pricing models are built on the assumption that an asset’s price volatility is mean-reverting. This means that while a stock’s volatility may temporarily spike above or fall below its mean, it typically remains bounded around its average level.

Mean Reversion in Trading

In trading, mean reversion strategies aim to capitalize on extreme price changes in specific securities. These strategies assume that prices will revert to their previous state, offering opportunities for profit. This theory can be applied to both buying and selling, allowing traders to benefit from unexpected upswings and protect against abnormal lows.

Investors often use mean reversion in combination with forecasting techniques to identify optimal trading opportunities. By understanding the ranges within which asset prices tend to fluctuate, investors can make more informed decisions.

Limitations of Mean Reversion

While mean reversion is a powerful concept, it comes with limitations. Reversion to a normal pattern is not guaranteed, especially when unexpected events occur. Positive events like new product releases or developments can disrupt the mean reversion process, as can negative events like recalls and lawsuits.

In reality, an asset can experience mean reversion even in the face of extreme events. However, as with most activities in financial markets, there are no guarantees about how specific events will affect the overall attractiveness of particular securities.

Frequently Asked Questions

What is the history of mean reversion in finance?

Mean reversion has its roots in statistical analysis and has been widely applied in finance since the mid-20th century. Its earliest applications were in analyzing stock prices and economic indicators.

Can mean reversion be applied to all financial assets?

Mean reversion can be applied to various financial assets, including stocks, bonds, commodities, and currencies. However, its effectiveness may vary depending on the specific asset and market conditions.

How do investors calculate the mean in mean reversion?

The mean or average used in mean reversion analysis is typically calculated using historical data. Investors consider a specific time period, such as the past 50 days, and calculate the average price or return over that period to establish the mean.

What are some common indicators used in mean reversion strategies?

Common indicators used in mean reversion strategies include moving averages, Bollinger Bands, and relative strength index (RSI). These indicators help identify overbought or oversold conditions that may signal mean reversion opportunities.

Are there risks associated with mean reversion strategies?

Yes, there are risks involved in mean reversion strategies. While they can be profitable, there is no guarantee that prices will revert to the mean, especially in the presence of significant market events or fundamental changes in an asset’s value.

Can mean reversion be applied to long-term investing?

Mean reversion is often associated with short-term trading strategies. However, some investors use mean reversion principles as part of a broader long-term investment strategy to identify buying opportunities when assets have significantly deviated from their historical averages.

What are some alternative strategies to mean reversion?

Alternative strategies to mean reversion include trend-following strategies, momentum trading, and fundamental analysis. These strategies focus on different aspects of market behavior and can complement mean reversion approaches.

How can I learn more about mean reversion and its applications?

If you’re interested in diving deeper into mean reversion and its applications, consider enrolling in finance courses, reading academic papers, and exploring financial research institutions. Additionally, practicing with simulated trading platforms can help you gain practical experience.

Key takeaways

  • Mean reversion is a concept in finance where asset prices and returns tend to return to their long-term average levels over time.
  • It is used by investors to identify abnormal market activity and make informed trading decisions.
  • Mean reversion is not a guaranteed phenomenon and can be disrupted by unexpected events.
View Article Sources
  1. MEAN REVERSION – Institutes and Faculty of Actuaries
  2. Mean Reversion – Meaning, Strategy, Examples, Limitation – Wall Street Mojo
  3. Mean Reversion in Housing Markets – Harvard DASH