We study a multidimensional screening problem with minimal restrictions on valuations. Our ?-relaxation of the constraints excludes bunching and cycles in the graph of active incentive-compatibility constraints. Therefore, the Lagrange multipliers do exist and enable us in characterizing...

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....

We study general discrete-types multidimensional screening without any noticeable restrictions on valuations, using instead epsilon-relaxation of the incentive-compatibility constraints. Any active (becoming equality) constraint can be perceived as "envy" arc from one type to another, so the set...

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. Firm profit and firm size may increase or decrease with market integration depending on the degree of asymmetry between countries. The country in which capital is relatively...