The mistaken belief that independent random events are influenced by previous outcomes — expecting a "correction" after a streak of results in one direction.
Deeper Explanation
After a stock rises 10 days in a row, many investors expect a decline — as if the market "remembers" the winning streak and is due for correction. But if daily price changes are random, each day is independent. Past returns (in the short run) do not predict future returns through any mechanism resembling coin-flip correction. The gambler's fallacy causes investors to sell winners prematurely (expecting reversal) and hold losers hoping for a bounce that statistics do not support. Distinguish the gambler's fallacy (no underlying cause for mean reversion) from genuine mean reversion (where there is a fundamental basis, such as cyclical earnings or overstretched valuation).
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