We generalize the usual screening approach and conditions for efficiency-at-the-top and acyclic property from linear to fixed-plus-separable or concave costs and multidimensional commodities. But under non-concave costs, like capacity constraints, an example shows a cycle in the solution graph....

Using linear demands for two types of consumers, this note shows why discounts are ubiquitous and premia are rare. By observing premia, one can infer that the package sold at premium is undistorted and the single-crossing condition must hold.

Examining a standard monopolistic competition model with unspecified utility/cost functions, we find necessary and sufficient conditions on their elasticities for welfare losses to arise from trade or market expansion. Two numerical examples explain the losses (under unrealistic elasticities).

We develop a two-factor, two-sector trade model of monopolistic competition with variable elasticity of substitution. Firms' profits and sizes may increase or decrease with market integration depending on the degree of asymmetry between countries. The country in which capital is relatively...

We propose a general model of monopolistic competition and derive a complete characterization of the market equilibrium based on an Arrow-Pratt measure of concavity of the utility, interpreted as the relative love for variety. When the relative love for variety increases with the consumption...