Finite population noncooperative games with linear-quadratic utilities, where each player decides how much action she exerts, can be interpreted as a network game with local payoff complementarities, together with a globally uniform payoff substitutability component and an own-concavity effect. For these games, the Nash equilibrium action of each player is proportional to her Bonacich centrality in the network of local complementarities, thus establishing a bridge with the sociology literature on social networks. This Bonacich-Nash linkage implies that aggregate equilibrium increases with network size and density. We then analyze a policy that consists of targeting the key player, that is, the player who, once removed, leads to the optimal change in aggregate activity. We provide a geometric characterization of the key player identified with an intercentrality measure, which takes into account both a player's centrality and her contribution to the centrality of the others. Copyright The Econometric Society 2006.

This paper studies whether structural properties of friendship networks affect individual outcomes in education. We first develop a model that shows that, at the Nash equilibrium, the outcome of each individual embedded in a network is proportional to her Katz-Bonacich centrality measure. This measure takes into account both direct and indirect friends of each individual but puts less weight to her distant friends. We then bring the model to the data by using a very detailed dataset of adolescent friendship networks. We first characterize the exact conditions on the geometry of the peer network, so that the model is fully identified. We then show that, after controlling for observable individual characteristics and unobservable network specific factors, the individual's position in a network (as measured by her Katz-Bonacich centrality) is a key determinant of her level of activity. A standard deviation increase in the Katz-Bonacich centrality increases the pupil school performance by more than 7 percent of one standard deviation.

No abstract

Summary. The spatial mismatch hypothesis (SMH) argues that low-skilled minorities residing in US inner cities experience poor labour market outcomes because they are disconnected from suburban job opportunities. This assumption gave rise to an abundant empirical literature, which is rather supportive of the SMH. Surprisingly, it is only recently that theoretical models have emerged, which probably explains why the mechanisms of spatial mismatch have long remained unclear and not properly tested. This article presents relevant facts, reviews the theoretical models of spatial mismatch, confronts their predictions with available empirical results and indicates which mechanisms deserve further empirical tests.