Implicit contracts are nontrivial Nash equilibria to the post-hiring trading game between a worker and the employer. These are supported by intrafirm, rather than labor market, reputations. The existence of an implicit contract that supports efficient trade is proved in a simple model.

Labour mobility may be caused by shifts in the derived demand for labour on the part of firms or sectors, or it may be caused by mismatches between workers and their jobs. Both reasons may be important, and this paper merges them into one model. It explores the consequences for (a) wage-tenure relationships and (b) the issue of sluggishness of wages caused by the implied selectivity of workers into preferred jobs and sectors.

We integrate the optimal sequential and the optimal sample-size search strategies. In contrast to the existing search literature in which individuals specialize in either search or work, the model in this paper allows for an optimal choice of search intensity that results in individuals' choosing to work and search simultaneously. The existing sequential search strategy literature follows optimal stopping theory in treating work as an absorbing state. We do not, however, require the searcher to stay in a job once it has been accepted but derive this behavior as a result of the searcher's optimization problem.

Labor market intermediaries play an important role in turnover in many labor markets. This paper analyzes one class of such intermediaries, namely, search firms. We first model the hiring decision of the firm in both succession and replacement planning. We show that employers will, in equilibrium, use search firms to find new hires even where the search firms have no technological advantage in search. This can be interpreted as being due to the search firms' ability to diversify away sampling risk.