Scaling law in a stable urban system of Japan

Scaling law quantifies nonlinear relationships between urban indicators and population size. Japan typifies populous Asian countries with a high urbanization level, but the applicability of scaling law in Japan was underexplored. Here, we address this gap by analyzing over 50 urban indicators across more than 1700 municipalities, encompassing education, dwelling, economy, health, and employment sectors. Results revealed a distinctive stability in Japan's urban system, with minimal variations in scaling exponents and residuals over time (2005–2020), which is different from rapidly urbanizing systems. Despite most indicators following expected scaling regimes, the sub-linear scaling relationship for financial revenue deviated from the theoretical expectation due to unique local tax policies. Furthermore, scale-adjusted indicators reveal significant spatial clusters, with central Japan showing enhanced performance in employment and northeastern cities excelling in taxpayer income. Our findings contributed to understanding urban scaling law in highly urbanized mature systems. The stability of urban systems promises predictability, highlighting scaling law as a theoretical guide in urban governance, but should also be combined with local policies.