Chai relocates segregation from the static geography of residence to the mobile geography of everyday activity. The paper’s decisive concept is activity space: the set of locations and movements through which residents actually encounter the city, rather than the residential unit conventionally used as the proxy for social separation. A longitudinal comparison of Beijing residents across housing categories demonstrates that segregation changes as built environments, mobility practices and institutional conditions change over time. The methodological operation is therefore double: spatial units are expanded beyond the home, while temporal comparison replaces a single cross-sectional snapshot. This exposes the analytical cost of treating urban social structure as geographically fixed. The paper also distinguishes transformations associated with changing built form from those linked to institutional legacies such as danwei and housing regulation. Its broader contribution is to urban geography’s increasing concern with dynamic exposure: social inequality is produced not only by where people live, but by the territories they repeatedly traverse, access and avoid.
URBANISM MEETS ART