Mean Reversion vs Trend Following: What the Evidence Says, and What Each One Costs
On SPY from 1994 to November 2026, neither a 200-day trend rule (9.4% a year) nor a 2-day RSI mean-reversion rule (7.0%) beat buy-and-hold (10.8%), and both roughly halved the worst fall. The trend rule won 44% of its trades and lagged in most years; the reversion rule won 69% and lost 25% in five weeks in 2020.















