The rapid, severe reversal of recent winners that occurs during specific hostile market regimes — the primary tail risk of momentum strategies and the reason regime detection is essential.
“In 40 years of studying the market, I never found a system that worked in all conditions. The investors who survived and thrived knew when their method was working and when it was not. Step aside when the tape turns against you. The market will always come back. Your capital may not. — William O'Neil”
— William O'Neil
Deeper Explanation
Momentum crashes are not random — they cluster in two specific market regimes. First, during sharp bear-market recoveries: when a severe market decline reverses abruptly, recent losers (which often include the most beaten-down, highest-short-interest names) rebound violently while recent winners — the momentum portfolio — continue to be sold. The momentum portfolio is temporarily on the wrong side of the most aggressive price movements in the market. Second, during extreme volatility spikes (India VIX above 40): when correlation across all assets rises sharply, trend-following signals fail because every trend is being overwhelmed by macro-driven forced selling. Academic research shows that the majority of momentum strategy's negative return periods are concentrated in these two regimes. The practical defences are: (1) absolute momentum as regime filter — reduce to cash when the broad market's own trend turns negative; (2) volatility-scaled position sizing — reduce position sizes as VIX rises, mechanically shrinking exposure when crash risk is highest; (3) time-horizon diversification — holding positions across 3-month, 6-month, and 12-month lookback windows smooths crash impact. Understanding momentum crashes transforms a strategy that looks dangerous on a historical drawdown chart into one with a manageable and navigable risk profile.
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