Our panel estimation technique allows us to combine countries that are represented in different surveys, as well as to include multiple observations for a single country. We recognize, however, that observations at different points in time or from different survey sources for a single country would not be independent. Therefore, we use the method of seemingly unrelated regression (SUR), which estimates (along with the coefficients) the correlations of the error terms in the equations for the different surveys for a given country. We also allow for differences in average survey results across the