Knowledge that Transforms

In this paper a theorem is developed giving necessary and sufficient conditions for the uniqueness of homogeneous product Cournot equilibria. The result appears to be the strongest to date and the first to involve both necessity and sufficiency. The theorem states than an equilibrium is unique if and only if the determinant of the Jacobian of marginal profits for firms producing positive output is positive at all equilibria. The result applies to the case where profit functions are twice differentiable and pseudoconcave, industry output can be bounded, the above Jacobian is non-singular at equilibria, and marginal profits are strictly negative for non-producing firms. The proof uses fixed point index theory from differential topology.

The author uses an equilibrium model of job matchings with a Nash wage equation to derive the response of wages and unemployment to productivity shock. By endogenizing labor's threat point, he shows that wages absorb fully permanent shocks but only partially temporary shocks. Hence, unemployment responds to perceived temporary shocks but not to permanent shocks. Copyright 1987 by The Review of Economic Studies Limited.

We study a dynamic model of duopoly in which firms choose both prices and quantities. If quantity (capacity) choices are relatively inflexible, firms generally carry excess (idle) capacity in equilibrium. Because of this enforcement cost, firms are unable to achieve monopoly levels. This contrasts with models in which which firms compete in either prices or quantities alone. On the other hand, if capacities are flexible firms may be able to sustain monopoly behaviour.

In a dynamic economy land and capital serve not only as factors of production but as assets which individuals use to transfer income from workinq periods to retirement. Static models of international trade based on the specific-factors model incorporate only the first of these. Once the second is recognized the supply of capital and evaluation of land can be derived from underlying intertemporal optimization behavior.

Imagine that one player, the “incumbent” competes with several “entrants”. Each entrant competes only with the incumbent, but observes play in all contests. Previous work shows that, as more and more entrants are added, the incumbent's reputation may dominate play of the game, if the entrants are faced in sequence. We identify conditions under which similar results obtain when the entrants are faced simultaneously, and we find specifications in which adding more simultaneous entrants has a dramatically different effect. We also show that, with either sequential or simultaneous play, incumbents need not prefer the situation in which their reputations can and do dominate play to the “informationally isolated” case in which each entrant observes only play in its own contest.