行业间工资差异和个体间差异【外文翻译】

外文翻译Inter-industry Wage Differences and IndividualHeterogeneityMaterial Source: Oxford Bulletin of Economics & Statistics V ol.66 Issue5,Dec 2004,p811-817Author: Carruth,Alan；Collier,William；Dickerson,AndyA major empirical regularity in the literature on the analysis of wage structure is the existence of large and persistent inter-industry wage differentials for workers of equal quality in equivalent occupations (Dickens and Katz, 1987; Krueger and Summers, 1987, 1988; Katz and Summers, 1989).These differentials exhibit a high degree of stability over time and appear to hold across a variety of countries with distinct institutional and structural arrangements (Gittleman and Wolff, 1993; Kahn, 1998). They also persist across different types of workers and establishment size. Such disparities are difficult to explain fully by the distribution of human capital accumulation across industries or by compensating differentials for non-pecuniary job attributes affecting the utility of workers. Their persistence is also inconsistent with the notion of transitory disequilibrium phenomena brought about by adjustments to labour supply or demand in the presence of imperfect short-run labour mobility. Accordingly, a number of non-competitive explanations have been proposed.In standard human capital theory, it is argued that job attributes that do not directly affect the utility of workers should have no effect on the determination of individual wages. In contrast, non-competitive theories of wage determination posit that such attributes can have a systematic effect on wages because they influence the optimal wage for firms to set. The purpose of these theories is to determine why firms may find it profitable (and are able) to pay wages higher than the market-clearing rate. In addition, such explanations must also explain why the importance of such factors differs by industry. A number of possibilities have been suggested.Efficiency wage models embody the need for high wages to elicit worker effort(Weiss, 1980; Akerlof, 1984; Shapiro and Stiglitz, 1984; Stiglitz, 1985). Union threat models (Dickens, 1986) underline the threat of collective action,whilst insider–outsider models (Solow, 1985; Lindbeck and Snower, 1986)stress the incumbent power of employees when bargaining for a share of industry rents. Each of these motivations predicts correlations between industry wage premia and industry characteristics consistent with the available evidence. However, none of these models is able to attest to all of the evidence.An alternative explanation is that observed wage differentials reflect unobserved differences in worker quality. Several studies (Murphy and Topel,1987; Krueger and Summers, 1988; Gibbons and Katz, 1992; Keane, 1993;Shippen, 1999; Abowd, Kramarz and Margalis, 1999) have utilized longitudinal data and fixed-effects models to test this hypothesis, with mixed results. Krueger and Summers (1988), for example, present little evidence to support the importance of unobserved heterogeneity in the determination ofindustry pay. In contrast, Murphy and Topel (1987), Keane (1993), and Abowd et al. (1999) find that unobserved heterogeneity explains 66%, 84%,and approximately 90%, respectively, of the apparent differential in log-wages across industries. Gibbons and Katz (1992) provide an experiment that does not rule out an unobserved ability explanation, but another experiment is sympathetic to the Krueger and Summers (1988) thesis that true industry differentials exist across industries, even for identical workers.Identifying the true nature and source(s) of observed inter-industry wage differentials is important on both research and policy grounds and also with regard to individual welfare. Renewed interest in the structure of wages has occurred at a time when wage inequality in both the US and the UK is higher than at any other time in the past 50 years (Katz, Loveman and Blanchflower, 1995; Machin, 1996). This increased dispersion has occurred both between and within groups with the same observable characteristics. Competitive models of the labour market imply that changes in dispersion should be largely transitory in nature. Increased inequality, in this regard, may be considered as being shared amongst individuals. In contrast, non-competitive models of the labour market imply that such changes may be largely permanent. The acceptance of such explanations thus has significant positiveand normative implications.This paper sets out to examine the existence, magnitude and stability of inter-industry wage differentials for Britain using longitudinal data drawn from the first eight waves of the British Household Panel Survey (BHPS). The survey enablesus to examine cross-section, pooled and longitudinal evidence for British inter-industry wage differentials between 1991 and 1998. There are extremely few panel studies of the inter-industry wage structure in the existing literature and, to our knowledge, only two for Britain. Hildreth (1995) presents cross-sectional and longitudinal evidence based on the first two waves of the BHPS. Benito (2000) extends this analysis across the first four waves of the BHPS whilst providing some additional innovative analysis concerning industry profitability. Both of these studies present evidence that much of the cross-sectional variation in wages attributed to industry affiliation can be accounted for by unobserved individual heterogeneity captured in fixed-effects estimation. However, both studies focus solely on one-digit industry affiliation and, combined with the fact that they have relatively few waves of data, rely on a relatively small number of industry switchers. They also do not account for measurement error which is known to interfere in panel approaches to estimation much more severely than cross-sectional estimation, especially when the number of switchers is small (see, e.g. Chowdhury and Nickell, 1985; Swaffield, 2001).This study advances the analysis of this topic by explicitly addressing the role of unobserved heterogeneity as an explanation of observed inter-industry differentials, whilst taking account of both industry aggregation and measurement error. Utilizing eight waves of BHPS data for both one- and two-digit industry affiliation permits a greater number of inter-industry transitions to be observed and hence allows us to estimate the crucial individual effects more accurately. By using a method of estimation attributed to Haisken-DeNew and Schmidt (1997) we are also able to provide a unique estimate of inter-industry wage dispersion. In contrast, in the Krueger andSummers (1988) methodology used by Benito (2000) and Hildreth (1995) inter alia, the measurement of inter-industry wage dispersion is a function of the omitted industry, which means that studies which use this method are often not comparable because different base industries have been chosen by the researchers. In addition, we explicitly investigate the impact that measurement errors in industry affiliation may have on our results.The additional waves provide a more robust test for the persistence and stability of the inter-industry differentials over time, and hence allow us to investigate a number of alternative explanations deemed important in the empirical debate. Our results show that differences in wages can be largely‘explained’ by observed and unobserved individual effects, along with a role for inter-industry differentials, andjob-specific characteristics. The key to this substantial improvement in explanation over the cross-section literature on individual wages is the fixed-effects methodology that controls for unobserved individual heterogeneity. In addition, the control of unobserved individual traits considerably reduces the extent of inter-industry wage differentials.The importance of unobserved heterogeneity in wage determination is difficult to ascertain. Krueger and Summers (1988) adopt two methods to test for the presence of unobserved differences in labour quality. First, they compare cross-section wage equations for May 1979 Current Population Survey (CPS) data both with and without controls for human capital (age, gender, race,education, tenure and occupation). The inclusion of labour controls is reported to have no impact on estimated industry differentials.Secondly, they use matched CPS data sets along with the 1984 Displaced Workers Survey (DWS) to estimate first-difference equations on industry movers. The DWS provides a sample where the severance from the previous job is exogenous to the employee – caused by plant closure, for example. These estimates appear broadly similar to their cross-section results. Both methods thus lead the authors to reject arguments for unobserved differences in labour quality.Gibbons and Katz (1992) add some support to this conclusion. They estimate first-difference models using data from the DWS for the period 1984–86 and report that industry switchers appear to earn, on average, 97% of the relevant cross-section differential. The authors accordingly reject unobserved ability explanations and conclude that industry effects are indeed important in explaining inter-industry wages.Our aim is to investigate the role of unobserved heterogeneity as an explanation of the observed inter-industry differentials. We utilize genuine panel data (rather than matched data) and the improved methodology of Haisken-DeNew and Schmidt (1997) to show explicitly that much of the observed cross-section inter-industry wage differentials can be accounted for by observed and unobserved individual-specific effects. Using the BHPS implies that we can also control for observed job and workplace characteristics.Of course, it remains to be explained why these unobserved individualeffects should be correlated with industry affiliation, although we suggest some possible explanations in our discussion and conclusion.译文行业间工资差异和个体间差异资料来源: Oxford Bulletin of Economics & Statistics V ol.66 Issue5,Dec 2004,p811-817作者：Carruth Alan；Collier William；Dickerson Andy一个在文献中关于工资结构的分析中发现的主要经验规律是对于相同职业的相等质量员工存在大量而且持久的行业间工资差异(Dickens and Katz, 1987; Krueger and Summers, 1987, 1988; Katz and Summers, 1989)。