外文翻译
原文
Occupational Mobility and Wage Inequality
Material Source：The Review of Economic Studies
Author：Gueorgui Kambourov
In this article we argue that wage inequality and occupational mobility are intimately related. We are motivated by our empirical findings that human capital is occupation specific and that the fraction of workers switching occupations in the U.S. was as high as 16% a year in the early 1970’s and had increased to 21% by the mid-1990’s.We develop a general equilibrium model with occu pation-specific human capital and heterogeneous experience levels within occupations.
We find that the model, calibrated to match the level of occupational mobility in the 1970’s, accounts quite well for the level of (within group) wage inequality in that period. Next, we find that the model, calibrated to match the increase in occupational mobility, accounts for over 90% of the increase in wage inequality between the 1970’s and the 1990’s. The theory is also quantitatively consistent with the level a
nd increase in the short-term variability of earnings.
INTRODUCTION
Despite an active search for the reasons behind the large increase in (within-group) wage inequality in the U.S. over the last 30 years, identifying the culprit has proved elusive. In this paper we suggest that the increase in the variability of productivity shocks to occupations, coupled with the endogenous response of workers to this change, can account for most of the increase in within-group wage inequality.
Several facts, documented in detail in Section 2, characterize the changes in wage inequality in the U.S. from the early 1970’s to the mid-1990’s. (1) Inequality of hourly wages has increased over the period—the variance of logs has increased from 0·225 to 0·354, or 57%, while the Gini coefficient has increased from 0·258 to 0·346, or 34%.(2) Most of the increase in wage inequality was due to rising inequality within narrowly defined age–education subgroups.(3) The increase in wage inequality reflects increased dispersion throughout the entire wage distribution.
(4) Individual earnings became substantially more volatile.
In Kambourov and Manovskii (2008) we document that there was a considerable increase in the fraction of workers switching occupations (e.g. cook, accountant, chemical engineer) over the same period. We find that the annual rate of occupational mobility in the U.S. has increased from 16% in the early 1970’s to 21% in the mid-1990’s.In addition, in Kambourov and Manovskii(2009) we find substantial returns to tenure in an occupation—an increase in wages of at least 12% after five years of occupational experience, holding other observables constant. This finding is consistent with the results from other studies discussed in Section 2.2, which, using different methodologies and data from different countries, provide evidence consistent with the occupational specificity of human capital and with the importance of the occupational search process.
Occupational mobility and wage inequality are interrelated because occupational mobility affects the distribution of occupational tenure and, thus, of human capital. In addition, occupations are characterized by fluctuating levels of productivity and demand for their services. Occupation-specific human capital ties people to their occupations and makes switching them difficult. Thus, the cross-sectional wage dispersion depends, among other things, on the distribution of occupational tenure in the population, and on the distribution of workers across occupations with different productivities and demands.To evaluate the connection between occupational mobility and wage inequality, one needs a
n empirically grounded general equilibrium model in which occupational mobility and wage inequality are endogenously determined.
The model we develop is based on the equilibrium search frameworks of Lucas and Prescott(1974) and Alvarez and Veracierto (2000). In these models, agents can move between spatially separated local labour markets that the authors refer to as “islands”, and, although each local market is competitive, there are frictions in moving between locations.
We build on the random search environment in Alvarez and Veracierto (2000) but instead of adopting this spatial interpretation we think of “islands” as occupations. Further, we introduce worker heterogeneity with respect to their occupational experience levels and allow for occupation-specific human capital.
Thus, when an individual enters an occupation, she has no occupation-specific human capital. Then, given that she remains in that occupation, her level of human
capital increases over time. When an individual switches her occupation, she loses the specific human capital accumulated in her previous occupation.
Output and wages in each occupation are a function of the employed amount of effective labour. Occupations are subject to idiosyncratic productivity shocks. We argue that the variability of these shocks has increased from the early 1970’s to the mid-1990’s.
We quantify the effects of the increased variability of occupational productivity shocks in the following experiment. We calibrate the parameters of the model to match a number of observations for the early 1970’s. Next, keeping the rest of the parameters fixed, we calibrate the parameters governing the variability of the productivity shocks to occupations in order to match several facts on occupational mobility for the mid-1990’s. At no point in the calibration do we target wage inequality.
Two important results emerge from our analysis. The first result is that even though wage inequality is not targeted, the model, calibrated to match the facts on occupational mobility, generates wage inequality and wage instability similar to the within-group measures in the data.For example, the variance of log wages in the model is around 70% of its within-group counterpart in the data, while the log 90/10 ratio and the Gini coefficient in the model are around 90% of their respective within-group measures in the data. We show that the presence of occupation-specific human capital is of central importance for the model’s ability to generate substantial levels of wage dispersion—a version of the model without occupation-specific human capital, calibrated to the facts on occupational mobility, gene
rates only a small amount of wage dispersion. The second major result is that the model captures almost all of the increase in within-group wage inequality and the increase in the short-term volatility of log earnings.
A number of papers, including Bertola and Ichino (1995) and Ljungqvist and Sargent (1998), have argued that the economy became more turbulent between the 1970’s and the 1980’s.
Turbulence is typically defined as an unobservable increase in the rate of skill depreciation upon a job switch over the period. Despite the intuitive appeal of the notion of increased economic turbulence, identifying it in the data has proved difficult. We suggest that the observable increase in occupational mobility is one possible manifestation of the increased turbulence. We identify this part of the
increase in turbulence with the increased variability of the occupational productivity shocks.
Most of the research on the increase in wage inequality was concentrated on explaining the rise in the college premium (e.g. Krusell, Ohanian, Ríos-Rull and Violante, 2000) or in the experience premium (e.g. Jeong, Kim and Manovskii, 2008). The increase in the college or experience premia, however, each account for less than a third of the overall increase in inequality. A distinguishing feature of this paper is that it provides a theory of within-group inequality. In essence, we argue that a substantial part
of the variance of wages for individuals from the same age–education group is explained by the heterogeneity of their occupational experience and by the current level of demand for the services of the occupations in which these workers choose to be employed.
译文
职业流动与工资不平等
资料来源：经济研究回顾作者：G u e o r g u i K a m b o u r o v  在这篇文章中，我们提出了工资不平等与职业流动是密切相关的。根据经验调查结果，我们发现人力资本是带有职业特性的，在1970年初美国转换职业的劳动者比例达到每年16%，1990年中期这个比例上涨到21%。我们建立了一种总体均衡模型，这种模型附带有职业特征的人力资本与职业内的不平均经验水平。我们发现将这个模型校准成为与1970年职业移动性相符时，这种模型对那个阶段的（体内）不平等水平作出了非常好的解释。接着，我们发现将这个模型校准成为与职业流动性相符时，这个模型对1970年到1990年间90%的工资不平等增加做出了解释。这个理论也在数量上与收入短期变化性的水平与增长相一致。
介绍documented翻译
尽管对于（体内）过去三十年工资不平等性大幅度加剧背后原因的活跃搜索表明元凶证实难以捉摸。
在这篇文章中我们提出生产力的变化的增长冲击了各行各业，再加上劳动者对于这种变化的内在反应，可以说明体内工资不平等加剧的大部分原因。
在第二章中证明的一些事实描绘了从1970年初到1990年中旬美国工资不平等性的特征。（1）时薪的不平等在这个阶段不断加剧-记录的变化从0.225增长到了0.354，增长了57%，而基尼系数从0.258增长到0.346，增长了34%。（2）工资不平等中大多数加剧是由于狭窄定义的受教育水平子体的越来越不平
等。（3）工资不平等的加剧反映了贯穿整个工资分配中的加剧分散。（4）个人工资从实质上变得更不稳定。
在Kambourov和Manovskii2008年的研究中，我们可以证明在同一阶段劳动者转换工作（像是厨师、会计、化学工程师等）的比例有相当大的提高。我们发现在美国职业流动的年比率从1970年初的16%增长到了1990年中旬的21%。另外，在Kambourov和Manovskii2009年的研究中，我们到了关于职业维持时间的实质性回复—在有了5年工作经验，拥有了其他显著的恒量后，工资至少上涨12%。这个发现与2.2章中讨论的其他研究结果相一致，而那些其他研究是运用来自不同国家的不同方法论和资料进行的，提供的根据与人力资本的职业特性以及职业研究过程的重要性相一致。
职业流动与工资不平等是互相联系的，这是因为职业流动会影响职业任期的分配，因此也影响了人力资本的分配。此外，职业具有生产力水平和服务需求水平不同职业就不同的特点。职业特点的人力资本将
人们与他们的职业联系到了一起，让转换职业变得困难。此外，具有代表性的工资分配取决于体中职业任期的分配，并且取决于在不同生产力和需求的职业中劳动者的分配。为了评估职业流动与工资不平等之间的联系，这需要以经验为基础的总体均衡模型，在这个模型中职业流动与工资不平等是内在决定的。
我们建立的这个模型是在建立在卢卡斯和普莱斯考特1974年的均衡研究框架以及阿尔瓦雷斯和Veracierto2000年的均衡研究框架的基础之上。在这些模型中，代理商可以在当地单独的劳动力市场进行空间上的移动，作者将其称作“岛屿”，而且尽管每一个当地市场竞争都很激烈，但是两个位置之间的在移动时是有摩擦的。我们是建立在阿尔瓦雷斯和Veracierto2000年的研究中的随机搜寻环境之上，我们不能够接受空间解释，而是认为“岛屿”就是职业。而且我们通过劳动者不同的职业经验水平以及能够接受的具有职业特点的人力资本方面介绍劳动者的不均匀性。因此，当某人开始某项职业时，她没有带有职业特征的人力资本，那么只要她一直从事这项职业，她的人力资本就会随着时间而增加。当她转换职业时，她就会失去在以前的职业中所积累的人力资本。
每一个职业的输出和工资都随着有效劳动力雇员数量的变化而变化。职业取决于特殊生产力冲击。我们认为这种生产力的冲击的变化性已经从1970年初到1990年中旬得到了增长。
在下面的试验中我们量化了增长的职业生产力冲击的影响。我们将模型的参数调整成与1970年初的一些
观察值相匹配。接着，保持剩余参数固定不变，我们调整参数控制下的职业生产力冲击的变化性，从而使之1990年中旬的职业变化性的一些事实相匹配。
我们分析得出了两个重要的结果。第一个结果就是虽然工资不平等并不是

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