Private Choices in Public Health: Endogenous Behavioral Responses to Pandemic Risk

Epidemic control depends not only on policy mandates but also on endogenous behavioral responses—how individuals adjust private preventive actions to evolving risk. Using over 1.1 million county-day observations from 1,206 U.S. counties, we integrate high-frequency mobility data with local COVID-19 mortality to estimate the semi-elasticity of preventive behavior to mortality-driven risk perception. Fixed-effects regressions exploit within-county temporal variation, controlling for day-of-week and month effects, county-specific linear trends, and public health policies. Behavioral elasticity evolved as the pandemic progressed. Early in the pandemic, mortality-driven risk perception had only a limited effect on behavior (3.1% reduction in mobility per additional death per 10,000 residents, 7-day lag), while shelter-in-place mandates drove large declines (–10.16%). As uncertainty declined and individuals learned about transmission risks, behavioral responsiveness strengthened markedly, with mobility falling 7.8% per additional death (7-day lag per 10,000)—indicating that risk-calibrated adaptation supplanted broad precautionary withdrawal. By the post-vaccination stage, the mortality–mobility association was no longer significant, consistent with behavioral desensitization as perceived risk fell. To unpack the selective logic of prevention—when behavior most closely tracked perceived risk—we find that reductions were most pronounced in discretionary settings (–5.2% retail/recreation; –5.3% transit) but statistically insignificant in essential activities (–0.4% grocery/pharmacy) and low-risk outdoor spaces (–1.7% parks). Responsiveness weakened by roughly 0.5% per month, while shelter-in-place and mask mandates amplified mortality-driven behavioral responses by 2.8% and 4.7%. These findings highlight that voluntary, risk-responsive behavior—amplified by policy interventions—was pivotal to epidemic control.