Mean Reversion
Mean reversion is the idea that prices that stretch far from their average tend to return toward it, and strategies that trade on that assumption.
When a price moves unusually far, unusually fast, it often snaps back part of the way. Mean-reversion traders bet on that snap-back: buying after sharp drops and selling after sharp rises, expecting a return towards an average. It is the opposite of trend following, and it works best in sideways, range-bound markets. Its weakness is the rare move that keeps going — which is why risk control decides whether a mean-reversion strategy survives.
- Category
- Trading Strategies
- Reading time
- 5 min
- Also called
- Mean-reversion strategy, Reversion to the mean, Mean reverting
- Updated
Mean reversion in plain words
Think of a rubber band: stretch it and it pulls back.1 Mean-reversion traders treat prices the same way. If a stock falls 8% in three days without news, they expect some recovery towards its recent average.
Tools such as the RSI, Bollinger Bands and the distance from a moving average measure how stretched a price is. Traditionally, an RSI above 70 is considered overbought and below 30 oversold.2 See Relative Strength Index and Bollinger Bands.
How a mean-reversion trade works, step by step
Choose the mean
A moving average, a range midpoint or a fair-value estimate. See Moving Average.
Measure the stretch
RSI extremes, closes outside a Bollinger Band, or a set percentage away from the average.
Check the market type
Mean reversion works best in ranges; in strong trends, overbought or oversold readings can last a long time.2 See Range Trading.
Enter against the stretch
Buy after an oversold drop, sell or short after an overbought rise — ideally after a first sign of turning.
Target the mean
Exit near the average rather than hoping for a full reversal.
Always use a stop
The rare move that does not revert can be large. Define the maximum loss before entering. See Stop Loss.
Worked examples
Example 1 — Buying an oversold dip in a range
RangeA stock ranges between $45 and $55 around a 20-day average of $50. It drops to $46 with an RSI of 26. A trader buys at $46.20, stop $44.40, target the average $50.
| Risk | $1.80 a share |
| Reward to the mean | $3.80 a share |
| Reward-to-risk | ≈ 2.1 : 1 |
Within a clear range, buying the stretched low and selling at the middle offers a favourable trade.
Example 2 — The shape of results
ProfileA mean-reversion system: 65% winners averaging +0.9R, 35% losers averaging −1.2R (some stops gap).
| Expectancy | 0.65 × 0.9 − 0.35 × 1.2 = +0.165R |
Many small wins and fewer, larger losses — the mirror image of trend following. See Expectancy.
Example 3 — When it does not revert
No reversionA stock falls from $50 to $44 and looks oversold. A trader buys without a stop. The company then cuts guidance and the stock falls to $31.
| Loss per share | $44 − $31 = $13 |
| In R (if a $1.80 stop was planned) | ≈ −7.2R |
One unhedged “cheap” stock can wipe out dozens of small wins. “Oversold” can always become more oversold.
Stretched readings on the RSI
Mean reversion vs. trend following
| Aspect | Mean reversion | Trend following |
|---|---|---|
| Idea | Stretched prices return | Moves continue |
| Typical win rate | Higher | Lower |
| Typical loss profile | Rare large losses | Many small losses |
| Best markets | Ranges | Trends |
| Main danger | A trend that does not stop | Long sideways periods |
Where mean reversion is used
Range-bound stocks and indices
Buying near support and selling near resistance in established ranges. See Support and Resistance.
Short-term index trading
Sharp, news-free drops in broad indices have historically often been followed by bounces — not always.
Pairs trading
Trading the gap between two related assets, expecting it to close. See Pairs Trading.
Options selling
Many option-selling strategies implicitly bet that prices stay within a range.
Advantages and disadvantages
Advantages
- High win rates, which many traders find easier to follow.
- Clear targets at the mean.
- Works well in the sideways markets where trend systems struggle.
Disadvantages
- Occasional large losses when trends persist.
- Easy to confuse a trend change with a stretch.
- Gaps and news can blow through stops.
- Tempting to average down, which compounds losses. See Averaging Down and Averaging Up.
Going deeper
Read as far as you need. Each level builds on the one before it.
Cheap can get cheaper
Beginner
A falling price is not a reason to buy on its own. Mean reversion needs a defined mean, a measured stretch, a range context and a stop.
Filtering with the bigger trend
Intermediate
Many traders only take mean-reversion buys when the longer-term trend is up — buying short-term dips in a long-term uptrend — which overlaps with pullback trading. See Pullback.
Statistical mean reversion
Advanced
In quantitative work, mean reversion is tested statistically — for example with stationarity tests or the Hurst exponent — and is the basis of pairs and spread trading on cointegrated assets. See Autocorrelation, Hurst Exponent and Cointegration.
Common mistakes
Fading strong trends
In trends, overbought and oversold can persist for a long time.
No stop-loss
Mean-reversion losses are rare but large; stops are not optional.
Averaging down repeatedly
Adding to a loser that keeps falling turns a small error into a big one.
Targeting too far
Aim for the mean, not a full reversal.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Mean reversion bets that stretched prices return towards an average.
- It works best in ranges and worst in strong trends.
- Typical results: many small wins, occasional larger losses.
- Target the mean and always use a stop.
- “Oversold” is a description, not a guarantee of a bounce.
Frequently asked questions
Is mean reversion better than trend following?
What is the “mean” in mean reversion?
Does mean reversion work in crypto?
Further learning
- Relative Strength Index
The most common stretch measure.
- Bollinger Bands
Another way to see when price is far from its average.
- Trend Following
The opposite approach.
- Stop Loss
The protection mean reversion cannot do without.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- Fidelity. Bollinger Bands (opens in a new tab) Checked .
- Fidelity. Relative Strength Index (RSI) (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.