T HE hypothesis that geographical mobility of workers is primarily a response to economic incentives arising from disequilibria across spacially separated labor markets has received considerable attention in the theoretical literature on investment in human beings.' In this paper I outline a simple model of migration as an economic process, and provide an empirical test of the model using data on net migration out of the United States South.2 To preview the main results, the model of migration as a response to economic incentive is supported. Specifically, the results suggest that the present value of the expected income gain from moving out of the South is positively related to the probability of moving and provides a better explanation of migration than the more conventional income measure based on regional differences in current incomes. Further, the level of schooling appears to increase the effect of income gain on the probability of moving, and age appears to reduce it. Significant racial differences in the main determinants of net migration are apparent.3

THE growing disillusionment with compensatory education and other anti-poverty programs has given new life to an old theme in United States social theory: the poor are poor because they lack mental skills. Their poverty is particularly intractable because it is rooted in the genetic structure inherited from their parents who were also poor and mentally deficient.' An explanation of transmission of economic status from one generation to the next is thus found in the heritability of IQ. The idea is rtot new: an earlier wave of genetic interpretations of economic and ethnic inequality followed in the wake of the failures of the purportedly egalitarian educational reforms of the early 20th century Progressive Era.2 The liberal environmentalist counterattack against these interpretations was highly successful; among social scientists, and in the public eye, the genetic position was largely discredited.3 Since the late 1960's, however, public disillusionment with egalitarian social programs has been enhanced by the dissemination of the heritability research of Burt, Jensen, and others, supporting the scientific claims of the genetic interpretation of racial inequality and intergenerational immobility.4 Further evidence has been found in studies such as the Coleman Report which seemed to indicate that scholastic achievement in schools is not greatly influenced by the level of educational inputs and that differences among children prior to school entry explained most of the nonrandom variance in test scores.5 The version of the genetic argument to which we will address ourselves may be summarized by two propositions: First, that IQ, as measured on standard so-called intelligence tests, is highly heritable, and second, that IQ is a major determinant of income, occupational status, and other dimensions of economic success. If both propositions were correct, it could easily be shown that intergenerational immobility, as measured by the correlation between the economic status of parents and their (adult) children, is attributable in large measure to the genetic inheritance of IQ and its role in determining economic position. The first proposition concerning the heritability of IQ has received careful scrutiny; in fact, the current debate on IQ has been dominated by a concern with IQ's heritability, virtually to the exclusion of questions concerning its economic importance.6 In this paper we Received for publication October 10, 1972. Revision accepted for publication June 26, 1973. * An earlier version of this paper was presented at the Far Eastern Meetings of the Econometric Society in Tokyo, June 1970, and at the workshop sponsored by the Committee on Behavioral Research in Education of the National Academy of Science in Chicago in June 1971. We are grateful to the participants at these meetings for helpful suggestions. Many of the ideas in this paper were worked out jointly with Herbert Gintis. We are grateful to him for his help and to Zvi Griliches, Christopher Jencks, Barbara Roemer, Janice Weiss and the members of the Harvard seminar of the Union of Radical Political Economists. The research presented here was supported financially by the Ford Foundation. 1Jensen (1969) begins his article on the heritability of IQ with: Compensatory education has been tried, and apparently it has failed. The most explicit statement of the genetic interpretation of intergenerational immobility is Herrnstein (1971). For a critical review of Herrnstein's interpretation, see Bowles and Gintis (1973). 2Michael Katz notes the historical tendency of genetic interpretations of social inequality to gain popularity following the failure of educational reform movements (Katz, 1968). On the rise of the genetic interpretation of inequality towards the end of the Progressive Era, see Karier (1972). 3See, for example Hunt (1961). 4See Jensen (1969) and Burt (1958). For a critical review of Jensen's and Burt's estimates, see Light and Smith (1969), Jencks et al. (1972), and Kamin (1973). 5 Coleman et al. (1966). A critique of statistical bases of the Coleman Report can be found in Bowles and Levin (1968 and 1969). See also Mosteller and Moynihan (1972). 6 Information on the economic success or failure of individuals at either extreme of the IQ distribution -such as the data invoked by Herrnstein -tells us virtually nothing about the overall economic importance of IQ as a determinant of an individual's place in the distribution of income or stratification system.

A new measure of labor market tightness on workers' behavior--the employment rent--is modeled as a determinant of workplace conflict. An empirical estimate of the employment rent--workers' expected cost of job loss--is calculated. It is argued that the cost of job loss affects strike incidence. This relationship is tested by estimating an econometric model of strike incidence for the United States from 1955 to 1983. The cost of job loss is shown to explain a large percentage of the variation in strike incidence. The cost of job loss is a far superior explanatory variable than the unemployment rate, which is commonly used in strike models.