Recently gravity trade models are applied to disaggregated trade data. Here manyzeros are characteristic. In the presence of excess zeros usual Poisson Pseudo MaximumLikelihood (PPML) is still consistent, the variance covariance matrix howeveris invalid. Correct economic interpretation however...

Recently gravity trade models are applied to disaggregated trade data. Here many zeros are characteristic. In the presence of excess zeros usual Poisson Pseudo Maximum Likelihood (PPML) is still consistent, the variance covariance matrix however is invalid. Correct economic interpretation...