Maps of intergenerational mobility, early and late 20th century. The top map shows estimates of average adult personal income attainment of children born into households at 25th percentile of the national income distribution for the birth cohorts from 1904 to 1916 where income attainment is observed in 1950. The bottom map shows estimated average adult personal income attainment of children born into households at 25th percentile of the national income distribution for the birth cohorts from 1978 to 1983, where income attainment is observed in 2014-2015. Darker (blue) colours indicate childhood locations that are associated with higher income attainment among children from poorer backgrounds while lighter (yellow) colours show lower levels of upward income mobility. Credit: Connor et al.

New research has found that since the mid-20th Century, cities in America are no longer positive centres for social and economic mobility.

The study combined remote sensing and administrative data to find that since the 1950s, large, growing cities have ceased to be centres of upward social and economic mobility. 

Cities have been celebrated as places of innovation and social mobility but also as hotspots of inequality and poverty.

Dylan Shane Connor and colleagues measured how the size, density, and connectedness of urban areas in an American’s birth county predicted their social mobility across the 20th Century.

The results tell a tale of a waning relationship between urban development and intergenerational mobility.

In particular, increases in population density between 1920 and 1990 are associated with significant reductions in intergenerational mobility — the reverse of the pattern seen between 1920 and 1950.

The same reversal occurred for the relationship with inequality, which was reduced by urban expansion in the early 20th Century and increased by urban expansion in the late 20th Century.

Contemporary urban expansion also decreases average social capital, as quantified by indicators of community and civic engagement, membership in local organisations, altruism, and the density of friendship networks.

According to the authors, these weakening social links may explain why growing cities are no longer places of special opportunity for all. 

The study is published in PNAS Nexus.