Mean Reversion
Definition
Mean reversion is the trading concept that after an extreme price move away from an average (VWAP, a moving average, a prior range), price has a statistical tendency to return toward that average — allowing traders to fade overextended moves rather than chase them.
Example
“The stock was trading 8% above its 20-day moving average and 4 standard deviations above VWAP on no news — that kind of overextension rarely holds. I faded the spike and it retraced 60% of the move within 20 minutes.”
Detailed Explanation
Mean reversion is the opposing philosophy to trend following. Where trend followers say "buy strength and sell weakness," mean reversion traders say "buy weakness and sell strength — because extremes don't last." Both approaches can work; the key is identifying which regime the market is in. In a strong trending environment, mean reversion fades get run over. In a choppy, range-bound environment, mean reversion is the dominant behavior and trend-following breakouts keep failing. Reading the current market character is more important than having a rigid philosophical allegiance to either approach.
The tools for measuring "how extended" something is: standard deviation channels around a VWAP or moving average tell you whether price is 1, 2, or 3 standard deviations away from its average — extremes (2+ SD) are where mean reversion setups are most reliable. Bollinger Bands serve the same function. RSI overbought/oversold readings (above 70 or below 30, especially on longer timeframes) indicate potential reversal zones. The key is waiting for evidence that the extreme is actually exhausting — a series of smaller and smaller candles at the high, a reversal candle pattern (engulfing, pin bar), or a failure to make a new extreme on the next push.
Mean reversion trades require patience before entry and defined risk management because calling a top or bottom feels intuitive but often proves premature. The cardinal error is fading an overextended move too early and getting run over by continued momentum. The professional approach is to wait for the momentum to visibly stall — the candles shrink, volume dries up, a reversal candle forms — before positioning. Being right about the direction but early on the entry is often just as bad as being wrong. Let the market show you it's ready to revert rather than trying to pick the exact peak or trough.