Shifting Family Care Preferences: The Role of Elderly Care Service Legislation in Shaping Older Adults' Perceptions in China

China has actively promoted Elderly Care Service Legislation (ECSL) to address population aging, yet its potential role in reshaping older adults' family care norms remains underexplored. Using five waves of panel data (2014-2023) from the China Longitudinal Aging Social Survey, this study employs a staggered difference-in-differences approach to examine the causal effect of ECSL on older adults' family care preferences, as well as its underlying mechanisms and heterogeneous patterns. ECSL implementation significantly reduced the probability of holding traditional family care preferences by 4.5 percentage points, with robustness checks supporting causal interpretation. This effect was associated with increased willingness to use formal elderly care services, offering suggestive evidence for the institutional trust mechanism through which legislation reduces family care preferences. Effects were stronger among older adults with greater individual resources and those in better-resourced regions, underscoring risks of exacerbating inequalities and highlighting the need for equitable resource distribution and targeted support.