This paper studies the event-history approach to microeconometric programevaluation. We present a mixed semi-Markov event-history model, discussits application to program evaluation, and analyze its empirical content.The results of this paper provide fundamental insights in what can be...

In a large class of hazard models with proportional unobserved heterogeneity, the distribution of the heterogeneity among survivors converges to a gamma distribution. This convergence is often rapid. We derive this result as a general result for exponential mixtures and explore its implications...