Urban Expansion Contradicts Population and Household Decline: A Fundamental Study on Correlation Between Demographic Trends and Urban Components

The shrinking of a city evokes an image that the amount of the main urban components, such as public facilities, infrastructure, and built-up areas, also shrinks. However, in reality, even in so-called shrinking cities with declining population, physical and spatial expansion is reported to continue and remain growth-oriented. This study examines whether some main urban components are shrinking in response to population and household decline by analyzing 1709 municipalities in Japan, around 80% of which have already experienced population decline over the past decade (2012–2022). The analyses use two datasets disclosing total quantities of respective urban components at the municipal level in the two endpoint years of 2012 and 2022, employing some simple techniques: correlation, simple regression analysis, and cross-tabulation. The results reveal that public facilities, road networks, and urban areas were supplied accordingly during periods of population growth but no corresponding downsizing occurs during periods of population decline; instead, several population-declining municipalities witness continuous expansion of these three urban components, contradicting the decrease in population and households. This tendency will create an imbalance between population and urban components, raising concerns that excessive public facilities, infrastructure, and urban areas disproportionate to population decline will undermine the efficiency of urban services and increase the burden on administrative and fiscal operations.