Definition
Alpha Decay
Alpha decay is the gradual erosion of a strategy's edge over time as the market becomes more efficient, the signal is arbitraged away, or the strategy becomes crowded.
An Indian signal that once predicted returns can fade as more participants discover and trade it, or as market structure changes. Alpha decay forces quant funds to continually research new signals, since no edge lasts forever and live performance often deteriorates after publication or wider adoption.
Managing decay involves monitoring live versus backtested performance, retiring stale signals, and diversifying across many edges so the loss of any one is bearable. Distinguishing genuine decay from a temporary drawdown is hard but central to running a sustainable quant book.
Related terms
- OverfittingOverfitting, or curve-fitting, occurs when a strategy is tuned so closely to historical data that it captures random noise rather than a genuine pattern, and consequently fails on new data.
- Quantitative TradingQuantitative trading is an approach that uses mathematical models, statistics and computer algorithms to identify and exploit trading opportunities, replacing discretionary judgement with systematic, data-driven rules.
- Signal (Quantitative)A signal is a quantified indication, derived from price, fundamental or alternative data, that a security is likely to rise or fall, forming the predictive core of a systematic strategy.
- Strategy CapacityStrategy capacity is the maximum amount of capital a quant strategy can manage before its own trading impact and crowding erode the edge below an acceptable level.
Plain-English explainer from The Dispatch Investors Encyclopedia. General information, not financial advice.