国际贸易理论研究的新动向——基于异质企业的研究

主流国际贸易理论均基于同质企业的假定来分析国际贸易的原因和影响。近年来以Melitz为代表的经济学家开始将企业异质性纳入国际贸易理论研究。本文以被Helpman称为基石性的Melitz"贸易对行业内资源配置与生产率的影响"一文为基础,介绍当前"新"贸易理论①的主要理论框架、主要观点和贸易自由化的经济效应。     

Trade and technology adoption

This paper endogenizes firms' choices of production technology in what would be a standard Melitz model otherwise. The responses of firms' productivity to trade liberalization are heterogenous: exporters, on average, improve their level of technology adoption, whereas nonexporters downgrade their level of technology adoption. The degree to which firms adjust production technology depends on domestic market size, export destination market size, trade impediments, and export status. The conflicting empirical results of the impact of trade liberalization on exporters' productivity are rationalized by showing that changes in different trade costs (variable vs. fixed costs) affect firms' productivity differently. We calibrate the model's parameters to match firms' characteristics in the global economy. The results indicate that endogenous productivity increases the gains from trade liberalization.     

Structural estimation and solution of international trade models with heterogeneous firms

We present an empirical implementation of a general-equilibrium model of international trade with heterogeneous manufacturing firms. The theory underlying our model is consistent with Melitz (2003). A nonlinear structural estimation procedure identifies a set of core parameters and unobserved firm-level trade frictions that best fit the geographic pattern of trade. Our estimation model is consistent with the specified general equilibrium model, and we conduct general equilibrium counterfactual analyses to illustrate model responses. We first assess the economic effects of reductions in measured tariffs. Taking the simple-average welfare change across regions the Melitz structure indicates welfare gains from liberalization that are four times larger than in a standard trade policy simulation. Furthermore, when we compare the economic impact of tariff reductions with reductions in estimated fixed trade costs we find that policy measures affecting the fixed costs are of greater importance than tariff barriers.     

Making sense of Bolkestein-bashing: Trade liberalization under segmented labor markets

An increase in the range of tradable goods is analyzed in a two-country Dornbusch-Fischer-Samuelson style model, where labor cannot relocate to another sector upon a non-expected increase in the range of goods that can be traded.The effect of liberalization on the terms of trade tend to favor the poorer country (the “East”), if (as assumed) the most sophisticated goods are tradable before reform. Second, under ex-post liberalization, there exists a class of workers in the West who are harmed because they face competition from Eastern workers and cannot relocate to other activities. But if the East's economy is relatively small, their wage losses are not very large. Things are different, however, if there exist asymmetries in labor market institutions, such that upon reform, labor can relocate in the East but not in the West. Some workers in the West can then experience very large wage losses. Thus, rigid labor markets in the West magnify opposition to reform there.     

Openness,inequality and poverty: Endowments matter

Using tariffs as a measure of openness, this paper finds consistent evidence that the conditional effects of trade liberalization on inequality are correlated with relative factor endowments. Trade liberalization, measured by changes in tariff revenues, is associated with increases in inequality in countries well-endowed with highly skilled workers and capital or with workers that have very low education levels. Similar, although less robust, results are also obtained when decile data are used instead of the usual Gini coefficients. Taken together, the results are strongly supportive of the factor-proportions theory of trade and suggest that trade liberalization in poor countries where the share of the labor force with little education is high raises inequality. Simulation results also suggest that relatively small changes in inequality as measured by aggregate measures of inequality, like the Gini coefficient, are magnified when estimates are carried out using decile data.     

贸易自由化对中国城镇劳动力市场性别歧视的影响

贸易自由化既可缩小也可扩大性别工资差。绝大多数实证研究,例如Oosdendorp(2004),都采用的是较宏观的行业加总数据,并着重于职业性别工资差。然而,行业加总的职业工资不能控制教育水平和经验变量,因此很难判断性别工资差的变化到底来自个人特征因素还是贸易自由化。文章运用中国城镇居民家庭的微观数据,运用difference-in-difference的方法,在消除了不随时间改变的固定效应和随时间变化的系统冲击的基础上,检验了1988年到1995年中国第一次贸易自由化兴起时期,贸易开放度的变化对不同教育水平的性别工资差的影响。结果显示,这一时期贸易开放度和性别工资差之间的相互关系主要来源于进口开放度的变化:随着进口开放度的上升,低教育人群的性别工资差显著扩大,而高教育人群的性别工资差却呈现相反趋势。出口开放度的上升对低教育人群的性别工资差没有显著影响,但与进口开放度的上升一样,它缩小了高教育人群的性别工资差。     

Labor market institutions,firm-specific skills,and trade patterns

This paper studies how a country's labor market institutions, by affecting workers' skill acquisition, can shape its export patterns. I develop an open-economy model in which workers undertake non-contractible activities to acquire firm-specific skills on the job. In the model, labor market protection raises workers' incentives to acquire firm-specific skills relative to general skills, turning labor laws into a source of comparative advantage. In particular, the model shows that countries with more protective labor laws export relatively more in firm-specific skill-intensive sectors at both the intensive and extensive margins. To test the theoretical predictions, I construct sector proxies for the firm-specific and industry-specific skill intensity by estimating returns to firm tenure and industry tenure for different U.S. manufacturing sectors during the 1974–1993 period. By estimating sector-level gravity equations for 84 countries using the Helpman–Melitz–Rubinstein (2008) framework, I find evidence supporting the predicted effects of labor market institutions at both margins of exports.     

On the growth effects of North-South trade: the role of labor market flexibility

This paper examines the impact of intensified North-South intra-industry trade from a growth theoretic perspective. It incorporates unemployment into Helpman’s [Econometrica 61 (1993) 1247] model of North-South trade. We assume that those Northern workers who lose their jobs due to imitation remain unemployed for a given (expected) length of time, so that imitation in the South causes frictional unemployment. It is shown that the shape of the relation between the (exogenous) rate of imitation and the (endogenous) steady-state growth rate depends on the degree of labor market flexibility, as measured by the outflow rate from unemployment. It is monotonically increasing for high outflow rates, hump-shaped for intermediate outflow rates, and monotonically decreasing for low outflow rates. The realization of the potential growth gains from trade thus presupposes labor market flexibility, and the model is capable of accounting qualitatively for the divergent growth performances in the US and Europe in the recent past.     

Establishment heterogeneity,exporter dynamics,and the effects of trade liberalization

We study the effects of tariffs and iceberg trade costs in a two-sector dynamic variation of the Melitz (2003) model extended to include a sunk cost of exporting, establishment-level uncertainty in productivity, capital accumulation, and material usage. We calibrate the model to match both cross-sectional and dynamic aspects of US producers related to export participation and the establishment lifecycle. We find a tariff equivalent of fixed export costs of 30 percentage points. We also find that a sizeable share of export profits is a return to the organizational capital from investing in export capacity rather than creating an establishment. We use the model to estimate the effect of reducing tariffs on welfare, trade, and export participation. We find that eliminating an 8 percent tariff increases the ratio of trade to GDP from 3.9% to 7.4% and raises welfare by 1.02%. Along the transition, consumption overshoots its steady state, even as trade and the capital stock grow gradually, so that the change in steady state consumption understates the welfare gain. Models without a dynamic export decision generate more gradual aggregate transition dynamics and smaller gains from trade. Capital accumulation and material usage are important sources of the welfare gains to trade.     

Establishment heterogeneity,exporter dynamics,and the effects of trade liberalization

We study the effects of tariffs and iceberg trade costs in a two-sector dynamic variation of the Melitz (2003) model extended to include a sunk cost of exporting, establishment-level uncertainty in productivity, capital accumulation, and material usage. We calibrate the model to match both cross-sectional and dynamic aspects of US producers related to export participation and the establishment lifecycle. We find a tariff equivalent of fixed export costs of 30 percentage points. We also find that a sizeable share of export profits is a return to the organizational capital from investing in export capacity rather than creating an establishment. We use the model to estimate the effect of reducing tariffs on welfare, trade, and export participation. We find that eliminating an 8 percent tariff increases the ratio of trade to GDP from 3.9% to 7.4% and raises welfare by 1.02%. Along the transition, consumption overshoots its steady state, even as trade and the capital stock grow gradually, so that the change in steady state consumption understates the welfare gain. Models without a dynamic export decision generate more gradual aggregate transition dynamics and smaller gains from trade. Capital accumulation and material usage are important sources of the welfare gains to trade.     

Trade and industrial location with heterogeneous labor

It is shown in the context of a new economic geography model that when labor is heterogeneous trade liberalization may lead to industrial agglomeration and inter-regional trade. Labor heterogeneity gives local monopsony power to firms but also introduces variations in the quality of the job match. Matches are likely to be better when there are more firms and workers in the local market, giving rise to an agglomeration force which can offset the forces against, trade costs and the erosion of monopsony power. A robust agglomeration equilibrium is derived analytically and its properties illustrated with numerical simulations.     

Globalization and firm level adjustment with imperfect labor markets

In a model with search generated unemployment and heterogeneity on both sides of the labor market, exporting firms are bigger and pay higher wages than other firms. Moreover, there is imperfect persistence in the decision to export and liberalization increases the wage gap between high- and low-skill workers. Openness can increase aggregate productivity in export-oriented markets while generating within-firm productivity losses for the weakest firms. In contrast, openness can lead to within-firm productivity gains for the weakest firms in import-competing industries.     

The dynamics of trade and competition

We estimate a version of the Melitz and Ottaviano [Melitz, Marc J. and Ottaviano, Gianmarco I.P., 2008, Market size, trade, and productivity, Review of Economic Studies 75(1), pp. 295-316.] model of international trade with firm heterogeneity. The model is constructed to yield testable implications for the dynamics of prices, productivity and markups as functions of openness to trade at a sectoral level. The theory lends itself naturally to a difference in differences estimation, with international differences in trade openness at the sector level reflecting international differences in the competitive structure of markets. Predictions are derived for the effects of both domestic and foreign openness on each economy. Using disaggregated data for EU manufacturing over the period 1989-1999 we find short run evidence that trade openness exerts a competitive effect, with prices and markups falling and productivity rising. The response of profit margins to openness has implications on the conduct of monetary policy. Consistent with the predictions of some recent theoretical models we find some, albeit weaker, support that the long run effects are more ambiguous and may even be anti-competitive. Domestic trade liberalization also appears to induce pro-competitive effects on overseas markets.     

Globalization and imperfect labor market sorting

This paper focuses on the ability of the labor market to efficiently match heterogeneous workers to jobs within a given industry and the role that globalization plays in that process. Using matched worker–firm data from Sweden, we find strong evidence that openness improves the matching between workers and firms in industries with greater comparative advantage. This suggests that there may be significant gains from globalization that have not been identified in the past — globalization may improve the efficiency of the matching process in the labor market. These results remain unchanged after adding controls for technical change at the industry level or measures of domestic anti-competitive regulations and product market competition. Our results are also robust to alternative measures of the degree of matching, openness, and the trade status of an industry.     

Migration and trade: Theory with an application to the Eastern-Western European integration

The remarkable increase in trade flows and in migratory flows of highly educated people are two important features of globalization of the last decades. This paper extends a two-country model of inter- and intra-industry trade to a rich environment featuring technological differences, skill differences and the possibility of international labor mobility. The model is used to explain the patterns of trade and migration as countries remove barriers to trade and to labor mobility. We parameterize the model to match the features of the Western and Eastern European members of the EU and analyze first the effects of the trade liberalization which occurred between 1989 and 2004, and then the gains and losses from migration which are expected to occur if legal barriers to labor mobility are substantially reduced. The lower barriers to migration would result in significant migration of skilled workers from Eastern European countries. Interestingly, this would not only benefit the migrants and most Western European workers but, via trade, it would also benefit the workers remaining in Eastern Europe.     

Trade and foreign direct investment-related impacts of Brexit

We offer a general-equilibrium analysis of Brexit incorporating the state-of-the-art differences in productivity and firms' selection within manufacturing sectors à la Melitz (Econometrica, 2003, 71 , 1695) and multinationals in services. Our results suggest that trade, output and average productivity diminish across most sectors in the UK and the Rest of the European Union (REU), as well as GDP, welfare, wages and capital remuneration. However, the UK loses more due to the missing preferential access to the huge EU market. Significant welfare losses along the extensive margin occur in the UK due to the lost imported varieties produced by highly productive European firms. These cannot be compensated by the new varieties of less productive domestic firms that enter the British market due to increased protectionism and reduced import competition. In addition, the emergence of barriers against multinationals, which is often ignored in previous studies, explains approximately one third of the negative effect in both the UK and REU. Furthermore, we show that the Brexit impact is about only half if we do not include both foreign direct investment barriers and Melitz structure. Thus, previous studies without these important model features would underestimate the Brexit impact significantly.     

Trade liberalization and the allocation of labor between households and markets in a poor country

We consider the relationship between relative price changes and the allocation of labor between households and the formal wage labor market in the context of Vietnam's liberalization of its rice trade in the 1990s. Many individuals in poor economies work within their own household rather than in formal labor markets. We find that larger rice price increases in a community are associated with declines in hours adults devote to work within the household and increases in time spent in the wage labor market. We also observe increased specialization in household economic activities accompanying these shifts in hours towards wage work. Our results are consistent with the idea that a growth in the extent of the market shifts production and labor from households to markets during development, thereby inducing gains from specialization. Thus, the reallocation of labor between households and markets in response to a trade liberalization might be an important component in understanding the link between trade and growth in very poor economies, currently the focus of the Doha WTO negotiation round.     

Globalization and imperfect labor market sorting

This paper focuses on the ability of the labor market to efficiently match heterogeneous workers to jobs within a given industry and the role that globalization plays in that process. Using matched worker–firm data from Sweden, we find strong evidence that openness improves the matching between workers and firms in industries with greater comparative advantage. This suggests that there may be significant gains from globalization that have not been identified in the past — globalization may improve the efficiency of the matching process in the labor market. These results remain unchanged after adding controls for technical change at the industry level or measures of domestic anti-competitive regulations and product market competition. Our results are also robust to alternative measures of the degree of matching, openness, and the trade status of an industry.     

Monopolistic competition: CES redux?

We study the competitive and reallocation effects of trade opening in monopolistic competition. To this purpose, we generalize the Melitz (2003) setup with heterogeneous firms and fixed and variable trade costs beyond the CES to the case of additively separable utility functions. We find that extensive margin (Melitz-type selection) effects are robust to relaxing the CES assumption. Intensive margin effects (market share reallocations across inframarginal firms) and competitive (markup) effects are instead fragile. An important implication is that measured productivity gains from trade opening are no longer ensured with non-CES preferences. We discuss our results in the light of alternative setups featuring non-additive preferences, strategic interaction and consumers' preference for an ideal variety.     

市场潜力、贸易自由化与地区工资差距

在新经济地理学的框架下,本文构建理论模型研究市场潜力和贸易自由化与地区工资差距的关系,根据中国1993－2012年的省际面板数据,采用工具变量二阶段最小二乘法实证检验市场潜力和贸易自由化对地区工资水平的影响效应。研究结果表明,市场潜力和贸易自由化对地区工资水平均有显著为正的影响作用,且二者还存在替代关系。进一步的分析发现,贸易自由化程度较高的沿海地区,其市场潜力对地区工资水平的影响较小,而在内陆地区则恰好相反。