An analysis of factors influencing population changes in relation to city size.
Aging populations and declining demographics are growing concerns worldwide, but the issue has intensified significantly in Japan. An alarming 36.21 million people, or 28.9% of the population, are aged 65 and over. Additionally, 74.6% of Japan’s 1,747 cities are classified as shrinking, with urban policies struggling to address the population decline. However, the factors influencing population changes across cities of different sizes remain unclear.
Dr. Haruka Kato, a junior associate professor at Osaka Metropolitan University, examined these multidimensional factors using the Economic, Social, and Educational (ESE) dataset, which is a cross-sectional dataset of 270 indicators of each Japanese city. This study used the machine-learning algorithm XGBoost, which analyzed the nonlinear relationships between the population change from 2005 to 2010 and the other 269 indicators.
Key Findings on City Sizes and Population Trends
The results revealed that most shrinking cities in Japan are medium-sized or small. Regarding the multidimensional factors, the rate of population change is strongly correlated with social-related indicators, such as changes among persons ages 0-14 in small cities, natural population change in medium-sized cities, and migration rates in large cities.
Additionally, population changes correlated with the financial strength index as an economic-related factor in medium-sized cities. Furthermore, population changes correlated with the designation of underpopulated areas as an urban-planning-related factor in small cities.
“These results imply that urban policies should be designed according to the size of the city,” said Dr. Kato. “Medium-sized cities should effectively formulate policies other than urban planning, such as childcare initiatives that would contribute to improvements in natural population change and the financial strength index. Meanwhile, small cities need to consider designating underpopulated areas.”
Reference: “Multidimensional factors correlated with population changes according to city size in Japan” by Haruka Kato, 18 August 2024, Environment and Planning B: Urban Analytics and City Science.
DOI: 10.1177/23998083241274381
The study was funded by the Japan Society for the Promotion of Science