In order to analyze careers both within and across firms, this paper proposes a matching model of the labor market that extends existing models of job assignment and learning about workers’ abilities. The model accounts for worker mobility across jobs and firms, for varying degrees of generality of ability, and for the possibility that firms affect the information they acquire about workers through job assignment. I characterize equilibrium assignment and wages, and show how, depending on how abilities and jobs are distributed across firms, equilibrium gives rise to widely varying patterns of job mobility within firms and turnover across firms, even if matching would be perfectly assortative in the absence of uncertainty. The implied job and wage dynamics display features that are consistent with a broad set of empirical findings on careers in firms and the labor market. In particular, workers can experience gradual promotions and wage increases following successful performance but few or no demotions when employed by the same firm. The model also produces turnover across firms and occupations after both successful and unsuccessful experiences, leading to wage increases or decreases following a firm or occupation change. Overall, the results in this paper provide a unified framework in which to interpret the dynamics of jobs and wages in firms and the labor market.

We analyze commitment to employment in an environment in which an infinitely lived firm faces a sequence of finitely lived workers who differ in their ability to produce output. A worker’s ability is initially unknown to both the worker and the firm. A worker’s effort affects the information on ability conveyed by his performance. We characterize equilibria and show that they display commitment to employment only when effort has a persistent but delayed impact on output. In this case, by providing insurance against early termination, commitment to employment encourages workers to exert effort, thus improving the firm’s ability to identify workers’ talent. The incentive value of commitment to retention helps explain the use of probationary appointments in environments in which there is uncertainty about individual ability.