Essays on Prices and Varieties in International Trade

摘要

The effects of international economic integration on the prices the firms charge and the number of varieties available for consumption is crucial for the welfare of consumers. This dissertation is a compilation of three essays, which, using both theory and empirical analysis, study the determinants of prices and of the number of varieties available for consumption.;Recent empirical work has shown that world trade is dominated by firms producing multiple products, and that a few large exporters, or superstars, account for most of a country's exports. These findings challenge traditional models of trade, in which each firm is small and produces a single product. The first two chapters of my dissertation study how the presence of multiproduct firms and superstars affects the predictions of the traditional models of trade.;In chapter one, I study the effects of international integration on consumers' welfare in the presence of large multiproduct exporters. The welfare of consumers depends on how large firms choose the number of the varieties they export - their product scope. I focus on two determinants of the scope of large exporters: income effects and cannibalization effects, namely the reduction in a firm's own sales following the introduction of a new variety. Several sources of data confirm the empirical relevance of the two determinants: 1) the product scope increases with the per capita income of the destination, and 2) as evidence of cannibalization effects, there exists a hump-shaped relationship between product scope and market share of a firm. I build a model of large multiproduct firms that generates results consistent with the empirical evidence. The model features firms competing oligopolistically and consumers with non-homothetic preferences. What are the effects of international integration on the welfare of consumers? To answer to this question, I derive a new formula for the welfare gains from trade that arise in a world of large multiproduct exporters. The formula highlights the contributions of income and cannibalization effects to the welfare gains from trade. In fact, models that ignore income effects would overestimate the gains from trade, while models that ignore cannibalization effects underestimate the gains. Moreover, neglecting cannibalization effects causes a sizable underestimation of the gains from trade in more concentrated industries.;A common prediction of standard models of multiproduct firms is that firm's total sales are proportional to the firm's scope. The underlying assumption is that the ability of a firm to produce efficiently a variety is proportional to its ability to introduce new varieties. In chapter two, joint with Mingzhi Xu, we document that such a prediction performs poorly in the data. Using Chinese firm-level data, we find a disconnect between sales and scope across firms within a destination: for any level of sales, there are several single product firms and wide scope firms. Moreover, firm-destination specific shocks explain more than 50% of the variation in scope across firms and destinations, and the scope of exporters conditional on sales depends on measurable characteristics of firms, such as capital intensity and R&D expenditures. We rationalize the three stylized facts in a model in which firms differ in their productivity and in their flexibility, namely the ability to introduce new varieties in a destination at low costs. The additional layer of heterogeneity has new implications for both intensive and extensive margins of trade.;While the first two chapters of the dissertation study how economic integration - modeled as a reduction in trade frictions - affects the welfare of consumers, in the third chapter, I examine those trade frictions, decomposing their nature and their effects. Recent research showed that deviations from the Law of One Price are starkly smaller within a currency union. Can a reduction in trade costs within a currency union explain this fact? I answer to this question in chapter three. I apply Heckscher's insight that transaction costs create bands of inaction in which price differences are not arbitraged away. Only when price differences exceed a certain threshold does arbitrage become profitable and prices begin to converge. A simple model of international arbitrage predicts that bands of inaction between two countries increase with trade costs and decline with the countries' sizes. I use monthly disaggregated price indices from 32 European countries from 1999 to 2016 and estimate the bands of inaction for the relative prices of 43 tradable commodities, using a Threshold Autoregressive Model. Currency unions reduce trade costs: the bands of inaction between countries that are in the European Monetary Union are 17% lower than the average band.