Diversity and Popularity in Social Networks

Homophily, the tendency of linked agents to have similar characteristics, is an im- portant feature of social networks. We present a new model of network formation that allows the linking process to depend on individuals types and study the impact of such a bias on the network structure. Our main results fall into three categories: (i) we compare the distributions of intra- and inter-group links in terms of stochastic dominance, (ii) we show how, at the group level, homophily depends on the groups size and the details of the formation process, and (iii) we understand precisely the determinants of local homophily at the individual level. Especially, we ¯nd that popular individuals have more diverse networks. Our results are supported empirically in the AddHealth data looking at networks of social connections between boys and girls.social networks, homophily, AddHealth, diversity, degree distributions

Title length

We document strong and robust negative correlations between the length of the title of an economics article and different measures of scientific quality. Analyzing all articles published between 1970 and 2011 and referenced in EconLit, we find that articles with shorter titles tend to be published in better journals, to be more cited and to be more innovative. These correlations hold controlling for unobserved time-invariant and observed time-varying characteristics of teams of authors

Peer effects and social networks in education

Abstract 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

POLLUTION ABATEMENT UNDER LEARNING BY DOING WITH HETEROGENEOUS COSTS

Environmental Economics and Policy,

Network Formation And Anti-Coordination Games

We study a setting in which individual players choose their partners as well as a mode of behavior in 2 x 2 anti-coordination games — games where a player's best response is to behave differently than the opponent. We characterize the nature of equilibrium networks as well as study the effects of network structure on individual behavior. Our analysis shows that both the network architecture and the induced behavior are crucially dependent on the value of the cost of forming links. In general, the equilibrium configurations are found to be neither unique nor efficient. This conclusion continues to hold if the population game is embedded in a standard evolutionary model of learning, since all equilibria turn out to be stochastically stable