We study a labour market in which firms can observe workers’ output but not their effort, and in which a worker’s productivity in a given firm depends on a worker-firm specific component, unobservable for the firm. Firms offer wage contracts that optimally trade off effort and wage costs. As...

Local network externalities are present when the utility of buying from a firm not only depends on the number of other customers (global network externalities), but also on their identity and/or characteristics. We explore the consequences of local network externalities within a framework where...

In an important paper, Aghion and Bolton (1987) argue that a buyer and a seller may agree on high liquidation damages in order to extract rents from future suppliers. As this may distort future trade, it may be socially wasteful. We argue that Aghion and Bolton's analysis is incomplete in some...

Do firms have the right incentives to innovate in the presence of productivity spillovers? This paper proposes an explicit model of spillovers through labor flows in a framework with search frictions. Firms can choose to innovate or to imitate by hiring a worker from a firm that has already...

The paper proposes a model of on-the-job search and industry dynamics in which search is directed. Firms permanently differ in productivity levels, their production function features constant returns to scale, and search costs are convex in search intensity. Wages are determined in a competitive...