Explained: How rural areas feed city growth

Using a field of research called urban scaling, which analyses the benefits and detriments of city life, the authors argue that population size is the single most important factor in the functioning of cities. For example, doubling city size reportedly raises total income, the number of patents, the number of residential moves, and the number of romantic breakups by roughly 115%. The extra 15% is referred to as the +15% phenomenon.

The researchers propose mathematical models to account for these regularities. Utilising Swedish register data, the study found that social interactions explain only half of the previously reported agglomeration effects, and that differences in population characteristics between metropolitan areas crucially drive the phenomenon. “Our results are of considerable policy relevance, because they identify the migration of talented people from smaller areas to larger cities as an important force behind observed agglomeration effects,” said Dr Keuschnigg.

Those moving from smaller areas to one of Sweden’s larger cities have, on average, 1.8 more years of education and their cognitive ability is 0.4 standard deviations higher than for those who stayed. (Source: Linköping University)