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Mean reversion is one of the oldest ideas in trading: prices that move too far from their typical level tend to come back toward it. It's the theoretical foundation behind the Short Reversion Scanner, so it's worth understanding on its own terms — including the one case where it doesn't hold.
What “reversion to the mean” actually means
A moving average is a rolling consensus price — roughly, where the stock has traded on average over some recent window. When price stretches well above that consensus, the stretch often reflects a temporary imbalance: a burst of buying pressure, a short squeeze, a news spike that pulled in more demand than usual. Mean reversion is the observation that these imbalances tend to fade once the exceptional pressure that caused them runs out, pulling price back toward the average it drifted away from.
Illustrative, not real price data. The idea: a stretch away from the typical range tends to fade back toward it as the pressure that caused the stretch runs its course.
Why it tends to work — most of the time
The mechanics are fairly intuitive. Short covering fades once the squeeze is over. Momentum buyers chasing a move eventually run out, because the pool of people willing to buy at ever-higher prices isn't infinite. Early holders start taking profit into strength. None of these forces are permanent, and as they fade, the imbalance that pushed price away from its average tends to fade with them.
Key takeaway: mean reversion is a tendency, not a law. It describes what usually happens to a temporary imbalance — it doesn't guarantee any single stock reverts on any particular day.
The exception that matters: trend, not deviation
The theory assumes the stretch away from the average is a temporary deviation. Sometimes it isn't — sometimes a stock is stretched because something genuinely changed (new information, a structural shift in demand) and the “overextension” is actually the early stage of a repricing that holds or keeps extending. There's no indicator, including this scanner, that reliably tells the difference between the two in real time. That's exactly why Short Reversion produces a candidate list rather than a signal: it flags stocks that fit the pattern mean reversion describes, and your chart work decides whether this particular stretch looks like a fading imbalance or something more durable.
TradeBeagle provides educational market-scanning tools. Not financial advice. No trade recommendations. Confirm every setup on your own chart and manage your own risk.