A family of integer programs is considered whose right-hand-sides lie on a given line segment L. This family is called a parametric integer program (PIP). Solving a (PIP) means finding an optimal solution for every program in the family. It is shown how a simple generalization of the...

The inefficiencies related to endogenous product creation and variety under monopolistic competition are two-fold: one static--the misalignment between consumers and producers regarding the value of a new variety; and one dynamic--time variation in markups. Quantitatively, the welfare costs of...

The rise of offshoring of intermediate inputs raises important questions for commercial policy. Do the distinguishing features of offshoring introduce novel reasons for trade policy intervention? Does offshoring create new problems of global policy cooperation whose solutions require...

In this paper we develop a monopolistic competition model where firms exercise their market power across multiple products. Even with CES preferences, markups are endogenous. Firms choose their optimal product scope by balancing the net profits from a new variety against the costs of...

This paper develops a general equilibrium model of multi-product firms and analyzes their behavior during trade liberalization. Firm productivity in a given product is modeled as a combination of firm-level "ability" and firm-product-level "expertise", both of which are stochastic and unknown...

For centuries, most international trade involved an exchange of complete goods. But, with recent improvements in transportation and communications technology, it increasingly entails different countries adding value to global supply chains, or what might be called "trade in tasks." We propose a...

This paper considers a dynamic, non-steady state environment in which wage dispersion exists and evolves in response to shocks. Workers do not observe firm productivity and firms do not commit to future wages, but there is on-the-job search for higher paying jobs. The model allows for firm...

This paper studies optimal policy in a business-cycle setting in which firms have a blurry understanding of the state of the economy due to informational or cognitive constraints. The latter are not only the source of nominal rigidity but also an impediment in the coordination of production. The...

Recent research has emphasized firm heterogeneity as a source of comparative advantage. Combining this approach with labor market frictions and worker heterogeneity provides a framework for studying the impact of trade on unemployment and inequality. This paper reviews this approach and reports...