Sizing up the individual market for health insurance: a comparison of survey and administrative data sources.

Provisions within the Affordable Care Act, including the introduction of subsidized, Exchange-based coverage for lower income Americans lacking access to employer coverage, are expected to greatly expand the size and importance of the individual market. Using multiple federal surveys and administrative data from the National Association of Insurance Commissioners, we generate national-, regional-, and state-level estimates of the individual market. In 2009, the number of nonelderly persons with individual coverage ranged from 9.55 million in the Medical Expenditure Panel Survey to 25.3 million in the American Community Survey. Notable differences also exist between survey estimates and National Association of Insurance Commissioners administrative counts, an outcome likely driven by variation in the type and measurement of individual coverage considered by surveys relative to administrative data. Future research evaluating the impact of the Affordable Care Act coverage provisions must be mindful of differences across surveys and administrative sources as it relates to the measurement of individual market coverage.