Why are trade agreements regional? I address this question in a model of oligopoly featuring product variety. Tariffs have the effect of manipulating a country's terms of trade and shifting profits towards the domestic market at the expense of foreign trade partners. Countries endogenously form...

When analyzing panel data using regression models, it is often reasonable to allow for time-varying covariate effects. We propose a novel approach to modelling time-varying coefficients in panel data regressions, which is based on penalized regression techniques. To illustrate the usefulness of...