What is a hidden Markov model in finance?

A model in which the market moves between unobserved states, each producing data with different statistics; the model infers which state is most likely.

What does a semi-Markov model add?

It models how long each regime lasts explicitly, which makes switches less jumpy and duration informative.

Which sectors do well in each regime?

The market-regimes pages measure it for every state since 1998, sector by sector.

Learn · Market regime detection

What is market regime detection?

Reviewed against the platform's code on Sep 23, 2026

Market regime detection classifies the state the market is in — for example calm or stressed volatility, benign or distressed credit, easy or tight policy — from observable data, so that forecasts, portfolio construction and risk limits can depend on the regime rather than treat all periods alike.

Why it matters

Relationships that hold in one regime often break in another: a strategy fitted across a credit expansion and a credit crisis alike learns an average that is right in neither.

How it works

Approaches range from rules on indicator levels to statistical models such as hidden Markov models and hidden semi-Markov models, which also model how long a regime tends to last and avoid switching on one noisy day.

How Opulence Alpha applies it

Opulence Alpha reads nine axes separately — volatility, sentiment, liquidity, credit, recession risk, the business cycle, inflation, real yields and monetary policy. Each axis's state comes from where its indicators sit in their own history, against percentile thresholds set for that axis; the nine are fused into one composite by a hidden semi-Markov model that switches only when the evidence clears a margin.

Today's nine-axis reading →

Related concepts

Regime-aware portfolio constructionRegime-aware portfolio construction lets the market regime shape how a portfolio is built and how much risk it takes — tightening in stress, never loosening automatically.Point-in-time dataPoint-in-time data records what was actually known on each date — filing dates, revisions, delistings — so a backtest cannot use information from the future. Lookahead and survivorship bias explained.Probabilistic forecastingProbabilistic forecasting publishes a distribution of possible returns, with calibrated intervals, instead of one expected number — so a position can be sized from its uncertainty.

All concepts →Sector behaviour in every market regime →

Questions

What is a hidden Markov model in finance?: A model in which the market moves between unobserved states, each producing data with different statistics; the model infers which state is most likely.
What does a semi-Markov model add?: It models how long each regime lasts explicitly, which makes switches less jumpy and duration informative.
Which sectors do well in each regime?: The market-regimes pages measure it for every state since 1998, sector by sector.

References

Hamilton, J. (1989). A New Approach to the Economic Analysis of Nonstationary Time Series and the Business Cycle. Econometrica.
Yu, S.-Z. (2010). Hidden semi-Markov models. Artificial Intelligence.

Educational content about research methods. Not investment advice.