Monte Carlo Likelihood-Ratio Tests for Markov Switching Models Staff analytical paper 2026-34 Gabriel Rodriguez Rondon, Jean-Marie Dufour This paper develops Monte Carlo likelihood-ratio tests for determining the number of regimes in Markov switching models. Unlike most existing procedures, which focus on testing one versus two regimes, the proposed methods allow testing an arbitrary number of regimes. They are valid in finite samples, robust to identification problems, and applicable to nonstationary, multivariate, and Markov switching GARCH models. Content Type(s): Staff research, Staff analytical paper JEL Code(s): C, C1, C12, C15, C2, C22, C3, C32, C4, C46, C5, C52, E, E3, E32 Research Theme(s): Models and tools, Econometric, statistical and computational methods, Economic models, Monetary policy, Real economy and forecasting