This article considers a model in which the productivity of a worker depends on his experience, ability, and position in the firm. It is shown that workers are sorted in positions based on comparative advantage. Furthermore, workers are induced to retire when productivity is equal to the value of time after adjusting for the reallocation of other workers by positions that would occur if the worker retired.

The primary goal of this article is to specify and estimate a structural simultaneous search model and then determine the empirical importance of simultaneous search. The results indicate that new labor force entrants search simultaneously. A secondary goal is to identify and estimate job offer arrival rates and wage offer rejection probabilities separately. The results indicate that a significant portion of unemployment spells are caused by slow arrival rates, but policies intended to speed arrival rates would increase the average length of unemployment spells.

In this paper, a firm maximizes profits over choices of wage schedules and hiring schedules in a model with (1) turnover costs, (2) a productivity function that depends on position and experience, and (3) employee utility functions that depend on monetary compensation and position. It is shown that firms may have reason to encourage employees to retire before their reservation wage is greater than their marginal product. However, if an alternative definition of marginal product is used, the usual relation holds.