How can we assess which countries select more experienced leaders for the highest oce? There is a wide variation in prior career paths of national leaders within, and even more so between, regime types. Obtaining a truly comparative measure of political experience is therefore a challenge and empirical studies have to rely on proxies instead. We propose PolEx, a measure of political experience that abstracts away from the details of the career paths and generalises based on duration of experience in politics, its quality, and its breadth. We draw on a novel data set of around 2,000 leaders from 1950 to 2017 and use a Bayesian latent variable model to estimate PolEx. We illustrate how the new measure can be used comparatively by addressing the question whether democracies select more experienced leaders. We find that while on average they do, this century the dierence with non-democracies has declined dramatically. Future research may leverage PolEx to investigate the role of prior political experience in, for example, policy-making and crisis management.