Inferring ghost cities on the globe in newly developed urban areas based on urban vitality with multi-source data

Due to rapid urbanization over the past 20 years, many newly developed areas have lagged in socio-economic maturity, creating an imbalance with older cities and leading to the rise of "ghost cities." However, due to the complexity of socio-economic factors, no global studies have measured this phenomenon. We propose a unified framework based on urban vitality theory and multi-source data, validated by various data sources. We derived 8841 natural cities globally with an area over 5 square kiloxmeters and divided each into new urban areas (developed after 2005) and old urban areas (developed before 2005). Urban vitality was gauged using the density of road networks, points of interest (POIs), and population density with 1 km resolution across morphological, functional, and social dimensions. By comparing urban vitality in new and old urban areas, we quantify the ghost cities index (GCI) globally using the theory of urban vitality for the first time. The results reveal that the vitality of new urban areas is 7.69% that of old ones. The top 5% (442) of cities were designated as ghost cities, a finding mirrored by news media and other research. This study sheds light on strategies for sustainable global urbanization, crucial for the United Nations' Sustainable Development Goals.