Table S1. Estimated parameters of the gravity equation with the Poisson model. Results for the year and country-specific fixed effects are not reported for space saving reasons. The symbols ***, **, and * indicate significant coefficients at 1, 5, and 10% levels of significance, respectively. The sector codes are described in Table 1, and the variable abbreviations are described in Table 2. The square correlation between actual and fitted values is commonly used in count models as a fit measure, as there is no closer equivalent to R² in linear models (Cameron & Trivedi, 2010).Table S1. Estimated parameters of the gravity equation with the Poisson model. Results for the year and country-specific fixed effects are not reported for space saving reasons. The symbols ***, **, and * indicate significant coefficients at 1, 5, and 10% levels of significance, respectively. The sector codes are described in Table 1, and the variable abbreviations are described in Table 2. The square correlation between actual and fitted values is commonly used in count models as a fit measure, as there is no closer equivalent to R² in linear models (Cameron & Trivedi, 2010).