Heterogeneity, Stratification, and Growth

We examine how economic stratification affects inequality and growth over time. We study economies where heterogeneous agents interact through local public goods or externalities (school funding, neighborhood effects) and economy-wide linkages (complementary skills, knowledge spillovers). We compare growth and welfare when families are stratified into homogeneous local communities and when they remain integrated. Segregation tends to minimize the losses from a given amount of heterogeneity, but integration reduces heterogeneity faster. Society may thus face an intertemporal tradeoff: mixing leads to slower growth in the short run, but to higher output or even productivity growth in the long run. This tradeoff occurs in particular when comparing local and national funding of education, which correspond to special cases of segregation and integration. More generally, we identify the key parameters which determine which structure is more efficient over short and long horizons. Particularly important are the degrees of complementarity in local and in global interactions.