Out of the woodwork: Enrolment spillovers in the Oregon health insurance experiment

We study the impact of expanded adult Medicaid eligibility on the enrolment of already-eligible children. We analyse the 2008 Oregon Medicaid lottery, in which some low-income uninsured adults were randomly selected to be allowed to apply for Medicaid. Children in these households were eligible for Medicaid irrespective of the lottery outcome. We estimate statistically significant but transitory impacts of adult lottery selection on child Medicaid enrolment: at three months after the lottery, for every nine adults who enrolled in Medicaid due to winning the lottery, one additional child also enrolled. Our results shed light on the existence, magnitude, and nature of so-called "woodwork effects."