Urban Structural Imbalance Under Rapid Expansion: Evidence from Service Accessibility and Housing Prices

This research examines the structural evolution and functional performance of urban spatial expansion in Changchun, Northeast China. Utilizing an integrated framework of the Adjusted Sprawl Index, Gaussian two-step floating catchment area (Gaussian 2SFCA) accessibility modeling, and XGBoost-SHAP machine learning, the study identifies a decoupled growth pattern where land development and infrastructure construction proceed without a corresponding increase in population density, reflecting a structural-demographic divergence. Empirical results demonstrate that land expansion reached a significant peak between 2015 and 2020, followed by a transition toward morphological equalization and stabilization after 2020. This process manifests as asynchronous urbanism, where the strategic deployment of physical infrastructure frameworks systematically precedes the functional integration of essential social services. The analysis reveals the emergence of localized service-value misalignment clusters in peripheral zones. The phenomenon represents a deviation from the traditional monocentric paradigm toward McCann’s framework of modern urban economics, as high residential valuations are sustained by social capital and institutional expectations despite physical service gaps. Within these clusters, the club realm and private enclosure function as critical forward-looking mechanisms, where the presence of influential groups signals future social and infrastructural investment. A negative interaction effect between property management levels and regional accessibility confirms that these private governance structures effectively substitute for maturing public resources. These findings suggest that future development should prioritize the functional integration of social systems over mere material expansion.