Smart Health and Elderly-Care Services and Labor-Market Outcomes: Evidence from a Multi-period Difference-in-Differences Analysis

China is aging at an unprecedented pace: by 2020, 264 million residents were aged 60 or above, and the traditional family-based model of old-age care is under mounting strain. Between 2017 and 2019, three central ministries jointly designated 33 Smart Health and Elderly-Care Application Demonstration Bases in three batches, covering 20 prefecture-level cities. This paper exploits the staggered designation as a quasi-natural experiment. Combining the China Family Panel Studies (CFPS) from 2014 to 2020 with prefecture-level statistics, a sample of 32,176 working-age adults in 126 cities is constructed, and multi-period difference-in-differences (DID) models are estimated. The pilot is found to raise the annual wage income of working-age residents by 11.4 percent on average, without reducing employment or working hours. The effect emerges only after designation, grows over time, and survives province-by-year fixed effects, the exclusion of long-term-care-insurance pilot cities, propensity-score-matched samples, and a 500-repetition placebo test. The wage gains are concentrated among women (16.8 percent) and rural-hukou workers (15.2 percent), the groups that typically shoulder family caregiving, suggesting that technology-enabled formal care relaxes the family-care constraint on labor supply and job quality.