Exodus: How Migration Is Changing Our World

Collier argues that moderate migration fosters societal benefits through diversity and economic stimulation, but rapid and large-scale migration can lead to reduced trust, cooperation, and social cohesion. The effects of migration follow an inverse-U shape, where gains diminish and losses escalate with increasing migration. 

Mutual regard, Collier believes, is a cornerstone of functional societies. Mutual regard is a sense of solidarity and trust among members of a community. This regard supports equitable redistribution and cooperation, but is fragile and easily eroded by cultural distance between migrants and the host population. Low trust among culturally distant migrant groups can persist in host societies, impeding integration and cooperation. For example, studies show that migrants often bring cultural norms shaped by their home societies, which may conflict with those of the host society. Collier references Robert Putnam’s findings that high levels of immigration reduce trust not only between groups, but also within the indigenous population, leading to a broader retreat from social engagement and solidarity.

Collier frames assimilation as the most practical and ethical solution, as it enables migrants to adopt the host society’s norms, language, and values, fostering trust, mutual regard, and a shared sense of identity.