Upper Limits of Densification: A Global Analysis of Vertical Urban Evolution from 1975-2025

초록

This paper investigates the influence of tall buildings on urban densification across 524 global cities with present-day populations over one million, from 1975 to 2025. Using a dataset that spans this period in five-year intervals and integrates satellite-derived metrics of built-up area and volume, I analyze how urban form changes in tandem with population growth. I assess this growth not only in surface area and total built volume, but also a proxy for average building height, and integrate a new variable: completions of individual buildings over 200 meters (200 m+). The findings show that while population growth often outpaces surface expansion—signalling densification—this is more closely aligned with increases in overall volume than with citywide average building height. In most cases, height growth is negatively correlated with densification. Globally, completions of 200 m+ buildings show a small but statistically significant negative relationship with density gains, suggesting that symbolic verticality does not equate to functional densification. These trends vary sharply by region and city growth intensity, with Asian megacities achieving density through midrise expansion and low-growth cities in Europe or the Americas relying more on iconic vertical retrofitting. The research challenges potentially flawed assumptions about tall buildings as universal density solutions and advocates for a more nuanced understanding of spatial efficiency.