" Relatively homogeneous societies invest more in public goods, indicating a higher level of public altruism. For example, the degree of ethnic homogeneity correlates with the government's share of gross domestic product as well as the average wealth of citizens. Case studies of the United States find that multi-ethnic societies are less charitable and less able to cooperate to develop public infrastructure. A recent multi-city study of municipal spending on public goods in the United States found that ethnically or racially diverse cities spend a smaller portion of their budgets and less per capita on public services than do the more homogeneous cities "

― , On Genetic Interests: Family, Ethnicity and Humanity in an Age of Mass Migration