Young people with private health insurance sometimes transition to the public health insurance safety net after they get sick, but popular sources of cross-sectional data obscure how frequently these transitions occur. We use longitudinal data on almost all hospital visits in New York from 1995...

We develop a model of selection that incorporates a key element of recent health reforms: an individual mandate. We identify a set of key parameters for welfare analysis, allowing us to model the welfare impact of the actual policy as well as to estimate the socially optimal penalty level. Using...