Poisson Gravity Model and Diff in diff

[Alessandro Mistretta]

Hi,
I'm working on a gravity model estimated using a poisson qmle (Santos Silva and Silvana Tenreyro); however i want to estimate a diff in diff model (pre-post effct) inside this kind of model. I know that d-i-d outside linear regression might have some problems, Do you think that in this particular case where PQMLE is utilized to log-linearize the gravity model i can apply a D-i-D design?
Thanks,
Alessandro

[Joao Santos Silva]

Dear Alessandro,

We used a DiD specification in this paper (strictly speaking, it is a ratio of ratios):

Santos Silva, J.M.C. and Tenreyro, S. (2010), Currency Unions in Prospect and Retrospect, Annual Review of Economics, 2, pp. 51-74.

Best wishes,

Joao
PS: Do let me know if you have trouble finding the paper.