The Changing Shape of Spatial Income Disparities in the United States

Abstract

Spatial income disparities have increased in the US since 1980, a pattern linked to major social, economic, and political challenges. Yet, today’s spatial inequality, and how it relates to the past, remains insufficiently well understood. The primary contribution of this article is to demonstrate a deep polarization in the American spatial system—yet one whose character differs from that commonly reported on in the literature. The increase in spatial inequality since 1980 is almost entirely driven by a small number of populous, economically important, and resiliently high-income superstar city-regions. But we also show that the rest of the system exhibits a long-run pattern of income convergence over the study period. A secondary contribution is historical: today’s superstars have sat durably atop the urban hierarchy since at least 1940. Third, we describe six distinctive pathways of development that regions follow between 1940 and 2019, with certain locations catching up, falling behind, and surging ahead. We explore the role played by initial endowments in driving locations down these pathways, finding population, education, industrial structure, and immigrant attraction to be key distinguishing features. These insights are enabled by a fourth contribution: methodologically, we use group-based trajectory modeling—an approach new to the field that integrates top-down and bottom-up views of the evolving national spatial system. We conclude by exploring implications for the mid-twenty-first century.