In the United States, households obtain health insurance through distinct market segments. To explore the economics of this segmentation, we consider the effects of pooling coverage provided through small employers and through individual marketplaces. We model households’ demand for insurance and health care along with insurers’ price setting to predict equilibrium choices and premiums. Applying our model to data from Oregon, we find that pooling can mitigate adverse selection in the individual market and benefit small group households without raising taxpayer costs. Our estimates provide insight into the effects of new regulations that allow employers to shift coverage to individual marketplaces.

How much are low- income individuals willing to pay for health insurance, and what are the implications for insurance markets? Using administrative data from Massachusetts’ subsidized insurance exchange, we exploit discontinuities in the subsidy schedule to estimate willingness to pay and costs of insurance among low- income adults. As subsidies decline, insurance take- up falls rapidly, dropping about 25 percent for each $40 increase in monthly enrollee premiums. Marginal enrollees tend to be lower- cost, indicating adverse selection into insurance. But across the entire distribution we can observe (approximately the bottom 70 percent of the willingness to pay distribution) enrollees’ willingness to pay is always less than half of their own expected costs that they impose on the insurer. As a result, we estimate that take- up will be highly incomplete even with generous subsidies. If enrollee premiums were 25 percent of insurers’ average costs, at most half of potential enrollees would buy insurance; even premiums subsidized to 10 percent of average costs would still leave at least 20 percent uninsured. We briefly consider potential explanations for these findings and their normative implications.