The Interaction of Partial Public Insurance Programs and Residual Private Insurance Markets: Evidence from the U.S. Medicare Program
研究政府提供部分公共保险（如美国联邦医疗保险）对未被覆盖风险（如处方药支出）的私人保险覆盖的影响，发现公共保险未显著减少私人保险覆盖，但改变了覆盖来源。
A ubiquitous form of government intervention in insurance markets is to provide compulsory, but partial, public insurance coverage and to allow voluntary purchases of supplementary private insurance. This paper investigates the effects of such programs on insurance coverage for the risks not covered by the public program, using the example of the US Medicare program. I find that Medicare does not have substantial effects-in either direction-on coverage in residual private insurance markets. In particular, there is no evidence that Medicare is associated with reductions in private insurance coverage for prescription drug expenditures, an expenditure risk not covered by Medicare. Medicare is, however, associated with a shift in the source of prescription drug coverage, from employer-provided coverage to Medicare HMOs.