Hi statalist,

I would like to clarify few things about using ppml on gravity data.

1. I'm trying to do a gravity model using patent data. My dependent variable is bilateral patent counts. independent variables are gdp, economic globalization, education of both country of origin and destination. I have included i.year, i.origin, i.dest for fixed effects and clustering by (dist). I noticed that my R-square is close to 0.92 and with additional variables it increases to 0.97. This is extremely high and should I worry about it?

2. Is there a way to get the adjusted r-square using ppml?

3. I'm interested in doing some mediation and moderation analysis on the gravity data but not sure of the codes to use.

Appreciate your advice.

Thanks.
Jaya