Mobility depends essentially on investment, which often occurs in environments in which individuals match (school) or will match after investing (the labor market). Where partners can transfer surplus to each other only imperfectly (NTU), the pattern of matching will typically be inefficient,...

This paper analyzes social group formation when agents are subject to peer effects within groups increasing human capital and instantaneous utility. When agents are heterogeneous on two dimensions, ability and social skills, and monetary payments are not feasible the model predicts segregation...