Fitting exponential regression models with two-way fixed effects

In this article, we introduce the commands twexp and twgravity, which implement the estimators developed in Jochmans (2017, Review of Economics and Statistics 99: 478{485) for exponential regression models with two-way fixed effects. twexp is applicable to generic nxm panel data. twgravity is written for the special case where the dataset is a cross-section on dyadic interactions between n agents. A prime example is cross-sectional bilateral trade data, where the model of interest is a gravity equation with importer and exporter eects. Both twexp and twgravity can deal with data where n and m are large, that is, where there are many xed effects. These commands use Mata and are fast to execute.