Representation and Hesitancy in Population Health Research: Evidence from a COVID-19 Antibody Study

We examine data from a serological study that randomized participation incentives ($0, $100, $500). Minority and poor households are underrepresented at lower incentives. We develop a framework that uses randomized incentives to disentangle non-contact and hesitancy and find that underrepresentation occurs because minority and poor households are more hesitant to participate, not because they are harder to contact. In particular, reservation payments for contacted households in minority and poor neighborhoods are substantially more likely to exceed $100. The $500 incentive closes hesitancy gaps and restores representativeness on observable dimensions including hospitalization and insurance rates, and a COVID-19 risk index.