A Social Network Analysis of Occupational Segregation

We develop a social network model of occupational segregation between different social groups, generated by the existence of positive inbreeding bias among individuals from the same group. If network referrals are important in getting a job, then expected inbreeding bias in the contact network structure induces different career choices for individuals from different social groups. This further translates into stable occupational segregation equilibria in the labour market. We derive the conditions for persistent wage and unemployment inequality in the segregation equilibria. Our framework is proposed as complementary to existing theories used to explain labour market inequalities between groups divided by race, ethnicity or genderSocial Networks; Inbreeding Bias; Occupational Segregation; Labour Market Inequality

Strong ties in a small world

This paper examines the celebrated "Strength of weak ties" theory of Granovetter(1973). We formalize the theory in terms of two hypotheses: one, for any threeplayers with two links present, the probability of a third link being present isincreasing in the strength of the two ties, and two, the removal of a weak tieincreases average distance in the network more than the removal of a strong tie. We test these hypotheses using data on the network of coauthorship amongeconomists. We find support for the hypothesis of transitivity of strong ties, but we reject thehypothesis that weak ties reduce distance more than strong ties do. We then identify two general features of networks which explain these findings:significant inequality in the distribution of connections across individuals andstronger ties among individuals who have more connections.network; strength of weak ties; core-periphery; co-authorship network

Competing Transport Networks

In a circular city model, I consider network design and pricing decisions for a single fast transport connection that faces competition from a slower but better accessible transport mode. To access the fast transport network individuals have to make complementary trips by slow mode. This fact has interesting implications on the location decisions. I show that in the presence of competition the profit-maximizing and socially optimal decision would be to cluster the two stations. By contrast, in the absence of competition both a profit-maximizing firm and a social planner would locate the two stations on opposite sides of the circle

Matching and network effects

The matching of individuals in teams is a key element in the functioning of an economy. The network of social ties can potentially transmit important information on abilities and reputations and also help mitigate matching frictions by facilitating interactions among ¿screened¿ individuals. We conjecture that the probability of i and j forming a team is falling in the distance between i and j in the network of existing social ties. The objective of this paper is to empirically test this conjecture. We examine the formation of coauthor relations among economists over a twenty year period. Our principal finding is that a new collaboration emerges faster among two researchers if they are ¿closer" in the existing coauthor network among economists. This proximity effect on collaboration is strong: being at a network distance of 2 instead of 3, for instance, raises the probability of initiating a collaboration by 27 percent. Research collaboration takes place in an environment where fairly detailed information concerning individual ability and productivity -reflected in publications, employment history, etc.- is publicly available. Our finding that social networks are powerful even in this setting suggests that they must affect matching processes more generally.coauthorship network, matching, network effects, network formation.

A Social Network Analysis of Occupational Segregation

We develop a social network model of occupational segregation between different social groups, generated by the existence of positive inbreeding bias among individuals from the same group. If network referrals are important for job search, then expected homophily in the contact network structure induces different career choices for individuals from different social groups. This further translates into stable occupational segregation equilibria in the labor market. We derive the conditions for wage and unemployment inequality in the segregation equilibria and characterize first and second best social welfare optima. Surprisingly, we find that socially optimal policies involve segregation.Social Networks, Homophily, Inbreeding Bias, Occupational Segregation, Labor Market Inequality, Social Welfare

Matching and Network Effects

This paper examines the existence and magnitude of network effects in the matching of workteams. We study the formation of co-author relations among economists over a thirty year period. Our principal finding is that a collaboration emerges faster among two authors if they are closer in the social network of economists. This proximity effect on collaboration is strong and robust but only affects initial collaboration. It has no positive influence on subsequent co-authorship. We also provide some evidence that matching depends on experience, junior authors being more likely to collaborate with senior authors.

Economics: An Emerging Small World?

The structures of social interaction affect individual behavior and economic performance in important ways. This leads us to ask: does the architecture of social interaction exhibit particular patterns and are these patterns stable over time? We examine interaction among economists by looking at the evolution of co-authorship relations over a thirty year period. We find that in the 1970's this world was quite fragmented with the largest interconnected group { the giant component { covering only 15% of the population. However, by the 1990's economics was much more integrated, with the giant component covering over 40% of the population. The average distance between individuals was small and declined over the period, leading us to conclude that economics is an emerging small world. A crucial stable feature of the network over this period is the existence of several stars (economists with many co-authors each of whom have few collaborators and rarely work among themselves). The world of economics is thus a collection of inter-linked stars. We also find that a growth in the average number of co-authors is the main reason behind the growth in the giant component and the fall in average distances within it. The second part of the paper develops a simple theoretical model of collaboration in economics. We find that an unequal distribution of collaborations and inter- linked stars arise naturally in this environment. Falling costs of communication and increasing credit for joint research lead to greater co-authorship and this supports a larger giant component.Small worlds, Networks, Global village

Economics: An Emerging Small World?

This paper examines the small world hypothesis. The first part of the paper presents empirical evidence on the evolution of a particular world: the world of journal publishing economists during the period 1970-2000. We find that in the 1970's the world of economics was a collection of islands, with the largest island having about 15% of the population. Two decades later, in the 1990's, the world of economics was much more integrated, with the largest island covering close to half the population. At the same time, the distance between individuals on the largest island had fallen significantly. Thus we believe that economics is an emerging small world. What is it about the network structure that makes the world small? An exploration of the micro aspects of the network yields three findings: one, the average number of co-authors is very small but increasing; two, the distribution of co-authors is very unequal; and three, there exist a number of ‘stars’, individuals who have a large number of co-authors (25 times the average number) most of whom do not write with each other. Thus the economics world is a set of inter-connected stars. We take the view that individuals decide on whether to work alone or with others; this means that individual incentives should help us understand why the economics world has the structure it does. The second part of the paper develops a simple theoretical model of co-authorship. The main finding of the model is that in the presence of productivity differentials and a shortage of high-productivity individuals, inter-connected stars will arise naturally in equilibrium. Falling costs of communication and increasing credit for joint research leads to greater co-authorship and this is consistent with the growth in the size of the giant component.

Strong Ties in a Small World

In this paper we test the celebrated `Strength of weak ties' theory of Granovetter (1973). We test two hypotheses on the network structure in a data set of collaborating economists. While we find support for the hypothesis of transitivity of strong ties, we reject the hypothesis that weak ties reduce distance more than strong ties do. We relate this surprising result to two different views of society. Whereas the classical view has been that society consists of different communities with strong ties within communities and weak ties between, the community of economic researchers has an interlinked star structure with strong ties between the stars. In such a world, strong ties are more important than weak ties

A Social Network Analysis of Occupational Segregation

This paper proposes a simple social network model of occupational segregation, generated by the existence of inbreeding bias among individuals of the same social group. If network referrals are important in getting a job, then expected inbreeding bias in the social structure results in different career choices for individuals from different social groups, which further translates into stable occupational segregation equilibria within the labour market. Our framework can be regarded as complementary to existing discrimination or rational bias theories used to explain persistent observed occupational disparities between various social groups