Despite the solid theoretical foundation on which the gravity model of bilateral trade is based, empirical implementation requires several assumptions which do not follow directly from the underlying theory. First, unobserved trade costs are assumed to be a (log-)linear function of observables....

Understanding trends in environmental quality is important for individuals and policymakers. Typically, trends in environmental quality are determined solely through comparisons of unconditional or conditional mean pollution levels. However, reaching unambiguous conclusions on the basis of only...