We study the joint processes of job mobility and wage growth among young men drawn from the Longitudinal Employee-Employer Data. Following individuals at three month intervals from their entry into the labor market, we track career patterns of job changing and the evolution of wages for up to 15 years. Following an initial period of weak attachment to both the labor force and particular employers, careers tend to stabilize in the sense of strong labor force attachment and increasing durability of jobs. During the first 10 years in the labor market, a typical young worker will work for seven employers, which accounts for about two-thirds of the total number of jobs he will hold in his career. The evolution of wages plays a key role in this transition to stable employment: we estimate that wage gains at job changes account for at least a third of early-career wage growth, and that the wage is the key determinant of job changing decisions among young workers. We conclude that the process of job changing for young workers, while apparantly haphazard, is a critical component of workers' move toward the stable employment relations that characterize mature careers.

The idea that wages rise relative to alternatives as job seniority accumulates is the foundation of the theory of specific human capital, as well as other widely accepted theories of compensation. The fact that persons with longer job tenures typically earn higher wages tends to support these views, yet this çvidence ignores the decisions that have brought individuals to the combination of wages, job tenure, and experience that are observed in survey data. Allowing for sources of bias generated by these decisions, this paper uses longitudinal data to estimate a lower bound on the avenge return to job seniority among adult men. I find that 10 years of current job seniority raises the wage of the typical male worker in the U.S. by over 25 percent. This is an estimate of what the typical worker would lose if his job were to end exogenously. Overall, the evidence implies that accumulation of specific capital is an important ingredient of the typical employment relationship, and of life-cycle earnings and productivity as well. Continuation of these relationships has substantial specific value for workers. The idea that wages rise relative to alternatives Over the duration of a job is the foundation for several important theories of productivity and compensation. Most prominently, a key prediction of Becker's (1964) model of investment in specific human capital is that wages rise with job tenure (seniority), leaving workers with a stake in the specific value of the employment relationship. Related theories of agency in durable employment relations (Becker and Stigler, 1974;Lazear, 1981) also generate deferred compensation that encourages workers' effort and improves performance.t Deferred compensation in the form of rising wages can also induce profitable self-selection of heterogeneous workers that enhances productivity (Salop and Salop, 1976). Other contracting models (Harris and Holmstrom, 1982; Freeman, 1977) produce qualitatively similar predictions for the shape of job-specific wage profiles. These ideas are sufficiently established that the assumption of rising wage profiles has become an accepted point of departure for subsequent work (e.g., Shleifer and Summers, 1988). RobertIn all of these models, a major component of earning capacity is both unique to a particular employment relationship and increasing in importance as the relationship ages. Senior workers would suffer substantial wage losses if their jobs were to end. Thus a common theme is specialization and, from a worker's perspective, the accumulation of job-specific capital. The credibility of this view is enhanced by the common finding from survey data that workers with longer job tenures typically earn more, which has been interpreted to mean that seniority raises earnings for the typical worker, and by related evidence thAt turnover rates (quits and layoffs) are strongly and negatively related to job tenure.2 These relationships are the empirical foundation for the view that specific capital is an important ingredient of life-cycle earning...

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We develop an economic framework for valuing improvements to health and life expectancy, based on individuals' willingness to pay. We then apply the framework to past and prospective reductions in mortality risks, both overall and for specific life-threatening diseases. We calculate (i) the social values of increased longevity for men and women over the 20th century; (ii) the social value of progress against various diseases after 1970; and (iii) the social value of potential future progress against various major categories of disease. The historical gains from increased longevity have been enormous. Over the 20th century, cumulative gains in life expectancy were worth over $1.2 million per person for both men and women. Between 1970 and 2000 increased longevity added about $3.2 trillion per year to national wealth, an uncounted value equal to about half of average annual GDP over the period. Reduced mortality from heart disease alone has increased the value of life by about $1.5 trillion per year since 1970. The potential gains from future innovations in health care are also extremely large. Even a modest 1 percent reduction in cancer mortality would be worth nearly $500 billion.