Social diversity and bridging identity

We investigate within a model of cultural transmission how policies or shocks that affect social diversity within a population affect social cohesion and segregation. We develop the concept of 'bridging identity', an individual trait that (i) positively affects utility in culturally diverse social groups but is immaterial in homogeneous groups and (ii) is fostered in those born in culturally diverse social groups but not in those born in homogeneous groups. We show that medium levels of immigration lead to higher bridging identity in the population; and, for a given immigration target, social segregation is decreasing in the time allowed for achieving this target. If the level and pace of immigration are attuned to existing levels of bridging identity, it is possible to sustain, for the long run, social groups that are culturally diverse. This contrasts with Schelling's models of residential segregation that typically lead to increasing segregation over time.