摘要：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
firmproduct- level “expertise”, both of which are stochastic and unknown prior
to the firm’s payment of a sunk cost of entry. Higher firm-level ability raises
a firm’s productivity across all products, which induces a positive correlation
between a firm’s intensive (output per product) and extensive (number of
products) margins. Trade liberalization fosters productivity growth within and
across firms and in aggregate by inducing firms to shed marginally productive
products and forcing the lowest-productivity firms to exit. Though exporters
produce a smaller range of products after liberalization, they increase the
share of products sold abroad as well as exports per product. All of these
adjustments are shown to be relatively more pronounced in countries’ comparative
advantage industries.
关键词：heterogeneous firms, endogenous product scope, love of variety, core competency
