Interdependent preferences and segregating equilibria

This paper shows that models where preferences of individuals depend not only on their allocations, but also on the well-being of other persons, can produce both large and testable effects. We study the allocation of workers with heterogeneous productivities to firms. We show that even small deviations from purely “selfish” preferences leads to widespread workplace skill segregation. This result holds for a broad class and distribution of social preferences. That is, workers of different abilities tend to work in different firms, as long as they care somewhat more about the utilities of workers who are “close”.

Social Networks in Labor Markets

Research in sociology and economics point to important role for social networks in labor markets. Social contacts mediate propagation of rich and reliable information among indi- viduals and thus help workers find jobs and employers find employees. Recent theoretical advances show that for agents connected through networks employment is positively cor- related across time and agents, unemployment exhibits duration dependence, and inequal- ity can persist. Recent empirical findings underscore nonlinearities in social interactions and potentially important effects of self-selection. Socioeconomic characteristics can explain substantial spatial dependence in unemployment.networks, labor markets, social connections, unemployment, proximity, spatial dependence, information networks, neighborhoods and jobs

Social Networks in Determining Employment and Wages: Patterns, Dynamics, and Inequality

We develop a model where agents obtain information about job opportunities through an explicitly modeled network of social contacts. We show that an improvement in the employment status of either an agent's direct or indirect contacts leads to an increase in the agent's employment probability and expected wages, in the sense of first order stochastic dominance. A similar effect results from an increase in the network contacts of an agent. In terms of dynamics and patterns, we show that employment is positively correlated across time and agents, and the same is true for wages. Moreover, unemployment exhibits persistence in the sense of duration dependence: the probability of obtaining a job decreases in the length of time that an agent has been unemployed. Finally, we examine inequality between two groups. If staying in the labor market is costly (in opportunity costs, education costs, or skills maintenance) and one group starts with a worse employment status or a smaller network, then that group's drop-out rate will be higher and their employment prospects and wages will be persistently below that of the other group.Networks, Labor Markets, Employment, Unemployment, Wages, Wage Inequality, Drop-Out Rates, Duration Dependence

Effort and synergies in network formation

The aim of this paper is to understand the interactions between productive effort and the creation of synergies that are the sources of technological collaboration agreements, agglomeration, social stratification, etc. We model this interaction in a way that allows us to characterize how agents devote resources to both activities. This permits a fullfledged equilibrium/welfare analysis of network formation with endogenous investment efforts and to derive unambiguous comparative statics results. In spite of its parsimony that ensures tractability, the model retains enough richness to replicate a (relatively) broad range of empirical regularities displayed by social and economic networks, and is directly estimable to recover is structural parameters.

Delinquent Networks

Delinquents are embedded in a network of relationships. Social ties among delinquents are modelled by means of a graph where delinquents compete for a booty and benefit from local interactions with their neighbors. Each delinquent decides in a non cooperative way how much delinquency effort he will exert. Using the network model developed by Ballester et al. (2006), we characterize the Nash equilibrium and derive an optimal enforcement policy, called the key-player policy, which targets the delinquent who, once removed, leads to the highest aggregate delinquency reduction. We then extend our characterization of optimal single player network removal for delinquency reduction, the key player, to optimal group removal, the key group. We also characterize and derive a policy that targets links rather than players. Finally, we endogenize the network connecting delinquents by allowing players to join the labor market instead of committing delinquent offenses. The key-player policy turns out to be much more complex since it depends on wages and on the structure of the network.Social networks, delinquency decision, key group, NP-hard problem, crime policies

Liberal democracy as the result of an "aborted" communist revolution

We propose a model of the transition from a ”big man” authoritarian regime to either a liberal democracy or a communist regime. An underground organization votes on whether to summon a mass event. If it is summoned, the organization members decide whether to put effort into the event. Higher effort makes regime change more likely, but it is individually risky. This creates the possibility, in principle, of high and low effort equilibria. But we show, using weak dominance arguments, that only the high effort equilibrium is ”credible.” Thus, internal party democracy is shown to be an efficiency enhancing element for political transitions. We extend the model to show that other internal organization aspects are key for the existence and welfare properties of this equilibrium. Finally we also show when is the process likely to end up in either democracy (and its ”quality”) or a full communist regime.

Peer Effects and Social Networks in Education

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 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.Centrality measure, peer influence, network structure, school performance

Social Preferences, Skill Segregation, and Wage Dynamics

Social Preferences, Skill Segregation, Internal Labor Market.

Social interactions and spillovers.

The aim of this paper is to provide a tractable model where both socialization (or network formation) and productive efforts can be analyzed simultaneously. This permits a fullfledged equilibrium/welfare analysis of network formation with endogenous productive efforts and heterogeneous agents. We show that there exist two stable interior equilibria, which we can Pareto rank. The socially efficient outcome lies between these two equilibria. When the intrinsic returns to production and socialization increase, all equilibrium actions decrease at the Pareto-superior equilibrium, while they increase at the Pareto-inferior equilibrium. In both cases, the percentage change in socialization effort is higher (in absolute value) than that of the productive effortPeer effects; Network formation; Welfare;

Una experiència amb Costa i Llobera a l’ESO

Abstract not availabl