Glossary
Regime Change
Persistent shift in the statistical properties of a market — volatility, correlation, mean return — that breaks the assumptions a strategy was designed under.
Sentivue Capital··4 min read
Regime change is a persistent shift in the statistical properties of a market — volatility, correlation structure, mean return, autocorrelation — that breaks the assumptions a strategy was designed under. Regime change is the dominant non-stationarity risk in systematic trading.
Examples
- 2007 → 2008: equity correlation jumped from ~0.4 to ~0.9; long-short equity strategies relying on dispersion broke.
- 2017 → 2018: crypto volatility regime shift broke trend-following parameters fitted on the prior bull run.
- 2020 March: liquidity regime change broke market-making models calibrated to normal book depth.
Detection
Regime change is hard to call in real time and obvious only in hindsight. Practical signals:
- Realized vol breakouts outside a multi-year band.
- Correlation regime shifts — a clustering test (e.g., Markov-switching model) flags when joint behavior changes.
- Cross-asset divergence — when historical relationships invert.
- Strategy-level drawdown signature that doesn't match historical worst-case.
Mitigation
- Walk-forward re-optimization with rolling windows that adapt to recent data (WFO).
- Strategy-level kill switches that flatten when realized drawdown breaches a threshold.
- Regime-conditioned models that switch parameters based on a classifier output.
- Diversification across regime sensitivities — pair trend-following (loves new regimes) with mean-reversion (likes old ones).