A new employee may work hard to build his reputation. However, the longer he is employed in his job, the more the firm will have learned about his ability. When there are career concerns, the incentives for an employee to influence the firm's perceptions of his ability decrease over time....

How large should a team be? We develop a basic group work model with endogenous team size. In teams that are too small, complementarities cannot develop properly, whereas in teams that are too large, the free-rider problem becomes overwhelming. If team members are overconfident, effort levels...