Curve Fitting in Trading: Why 92% Backtest Accuracy Becomes 35% Live Performance
You just bought a trading bot. The backtest shows 92% win rate over five years. The marketing video shows the developer's "live account" with perfect equity curves. You deploy it with $2,000, confident you've found the edge everyone else is missing. Three weeks later, your account is down 18%. The bot that won 92 out of 100 trades in the backtest is winning 6 out of 17 in your live account. What happened? Curve fitting the single biggest reason trading bots fail spectacularly after showing spectacular backtests. What Is Curve Fitting (And Why It Destroys Bots) Curve fitting (also called over-optimization) occurs when a trading strategy is tweaked and adjusted so extensively on historical data that it learns the specific noise and quirks of that past data rather than discovering genuine market principles that persist into the future. In simpler terms: The strategy memorized the test answers instead of learning the underlying concepts. Real example of curve fitting in ...