We introduce a dynamic statistical model for Skellam distributed random variables. The Skellam distribution can be obtained by taking differences between two Poisson distributed random variables. We treat cases where observations are measured over time and where possible serial correlation is...

In 2004, the German Social Health Insurance introduced a co-payment for the first doctor visit in a calendar quarter. I combine a structural model of health care demand and a difference-in-differences strategy to estimate the effect of that reform on the number of visits. In the model, the...