New Study Predicts Slower Global Urban Expansion by 2100

A new scientific study suggests that the rapid expansion of global cities might slow down by the end of this century. Although current trends show massive migration, researchers expect urban growth to decelerate over the coming decades. By 2100, only 38 percent of the global population will reside in cities exceeding one million inhabitants. This projection, which was published in PNAS, represents about 450 million fewer residents than standard trend models predict. This difference is substantially larger than the entire population of the United States. In 1975, only 11 percent of people lived in these large cities, compared to 24 percent today.

The research was conducted by scientists at the Complexity Science Hub and ETH Zurich. To track growth consistently, the team utilized satellite imagery and census records instead of administrative boundaries. According to researcher Andrea Musso, traditional boundaries are often misleading because cities expand beyond official limits. For instance, Paris is much larger than its administrative boundary, and New York is not just Manhattan. Consequently, the researchers divided the world into grid cells of roughly one square kilometer to monitor growth. They identified whether each cell was urban or rural based on population and building density.

The study reveals that urban systems follow a specific life cycle that determines their growth rates. In developing nations, large cities grew 7.3 percent faster than smaller towns between 1975 and 2025. People migrated to these massive hubs because employment opportunities, hospitals, and universities are usually concentrated there. However, this powerful magnetic pull weakens once a country achieves a higher level of urbanization. Consequently, cities in Europe and the Americas grew at the same rate as the national average. In large cities, people spend over twice as much time in traffic compared to small towns. Furthermore, residents are nearly three times more likely to contract diseases, yet they are twice as productive. According to Frank Neffke, this economic driver loses momentum as urbanization increases.