A researcher explored the complex, non-linear factors influencing population changes in relation to the size of cities. The findings suggest that in medium-sized cities, population variations are linked to an economic factor known as the financial strength index.
Globally, aging populations and declining numbers have been increasing, but Japan is experiencing this issue more acutely. An alarming 36.21 million residents, which makes up 28.9% of the total population, are aged 65 or older. In addition, 74.6% of Japan’s 1,747 cities are classified as losing population, with urban policies falling behind in addressing this trend. However, the specific factors influencing population changes across cities of different sizes remain unclear.
Dr. Haruka Kato, a junior associate professor at Osaka Metropolitan University, investigated these various factors by utilizing the Economic, Social, and Educational (ESE) dataset, a comprehensive collection of 270 indicators from each Japanese city. The study employed the XGBoost machine-learning algorithm to analyze the nonlinear connections between population changes from 2005 to 2010 and the other 269 indicators.
The analysis found that the majority of the cities experiencing population decline in Japan are either medium-sized or small. In terms of multidimensional factors, the population change rate closely aligns with social indicators, such as shifts in the 0-14 age group in smaller cities, natural population changes in medium-sized cities, and migration statistics in larger cities. Moreover, in medium-sized cities, the financial strength index was also found to correlate with population changes as an economic indicator. In smaller cities, population changes were associated with the classification of areas as underpopulated, a factor related to urban planning.
Dr. Kato stated, “These findings suggest that urban policies should be tailored to the size of the city.” She emphasized that medium-sized cities ought to devise policies beyond just urban planning, such as childcare programs, to help enhance natural population growth and bolster the financial strength index. At the same time, small cities should think about recognizing underpopulated regions.”
