“Matthew Effect” in Global Major Cities Over Decades: In the context of the spatiotemporal 3D urban expansion

Abstract Urbanization has surged over the past decades. Global major cities’ land urbanization and population urbanization have intensifying pressures on urban climate, public health, and energy consumption. A favorable vision for assessing urban habitats’ living conditions necessitates recognizing the evolution and current status of major global cities’ three-dimensional structure and spatiotemporal trajectories. However, a lack of high-resolution, long-term data hinders obtaining metrics reflecting living conditions. This study addresses this gap by generating a 30-meter resolution spatiotemporal three-dimensional urban expansion dataset for 2071 global major cities (1990–2020). Integrated with socioeconomic data, it reveals adherence to Zipf's Law, reflecting pronounced unequal development and a global-scale Matthew effect. Most cities fell within the 0–1 km³ volume range, with 12 cities and 41 cities’ volume > 9 km³ in 1990 and 2020, respectively. About two-thirds of major cities experienced building expansion rates exceeding population growth rates between 2000 and 2020. Per capita building volume correlates with the GDP. Africa is the only continent to witness a decline in per capita building volume over the past 20 years, indicating a further decline in the living conditions of urban residents. Focusing on internal building structures, an inequality index characterizes height diversity within cities. Asian cities exhibit the highest global inequality index, marked by supertall building additions. This study not only compares major cities' overall size and growth patterns in three dimensions but also analyzes the distribution of building heights within each city in detail. The findings contribute to identifying and addressing urbanization challenges, supporting habitat environmental assessments, and measuring progress toward sustainable goals.