Big cities have fueled inequality since mid 20th century, according to study
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PNAS Nexus
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) colors indicate childhood locations that are associated with higher income attainment among children from poorer backgrounds while lighter (yellow) colors show lower levels of upward income mobility. Credit: Connor et al.
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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) colors indicate childhood locations that are associated with higher income attainment among children from poorer backgrounds while lighter (yellow) colors show lower levels of upward income mobility. Credit: Connor et al.
A study combining remote sensing and administrative data finds that since the mid-20th century, large, growing cities have ceased to be centers 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. The study is in PNAS Nexus.
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 organizations, 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.
More information:
Dylan S Connor et al. Big cities fuel inequality within and across generations, PNAS Nexus (2025). .
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Since the mid-20th century, large cities have shifted from being centers of upward mobility to hubs of inequality. Increased population density from 1920 to 1990 correlates with reduced intergenerational mobility, reversing earlier trends. Urban expansion now also diminishes social capital, weakening community ties and civic engagement, which may explain the decline in cities as places of opportunity.
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