We assess the extent to which specialist doctors respond to local competition when setting prices (including extra-billings) in a fee-for-service system. We use an exhaustive panel data set to estimate physician reaction functions, exploiting exogenous changes in medical density and labor supply...

When a treatment in difference in differences (DD) is applied to a group of individuals with a time-constant qualifiÂ…cation/eligibility such as gender or race, there is no issue of choosing to be (un-)treated. But if the qualiÂ…fication is time-varying, then the individuals may alter...