Job matching, social network and word-of-mouth communication

Workers can find a job either directly or through personal contacts. From this micro scenario, we derive an aggregate matching function that has the standard properties but fails to be homogeneous of degree one. We show that, when the network size increases, on average, the unemployed workers hear about more vacancies through their social network. However, above a certain critical value, job matches decrease with network size. We then establish existence and uniqueness of the labor market equilibrium and study its properties. Finally, we demonstrate that the decentralized market equilibrium is not efficient because of both search and network externalities.