NBER Working Papers by Mark Shepard

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Working Papers

January 2017Price-Linked Subsidies and Health Insurance Markups
with Sonia P. Jaffe: w23104
Subsidies in many health insurance programs depend on prices set by competing insurers – as prices rise, so do subsidies. We study the economics of these “price-linked” subsidies compared to “fixed” subsidies set independently of market prices. We show that price-linked subsidies weaken price competition, leading to higher markups and subsidy costs for the government. We argue that price-linked subsidies make sense only if (1) there is uncertainty about costs/prices, and (2) optimal subsidies increase as prices rise. We propose two reasons why optimal health insurance subsidies may rise with prices: doing so both insures consumers against cost risk and indirectly links subsidies to market-wide shocks affecting the cost of “charity care” used by the uninsured. We evaluate these tradeoffs em...
November 2016The Evolution of Health Insurer Costs in Massachusetts, 2010-12
with Kate Ho, Ariel Pakes: w22835
We analyze the evolution of health insurer costs in Massachusetts between 2010-2012, paying particular attention to changes in the composition of enrollees. This was a period in which Health Maintenance Organizations (HMOs) increasingly used physician cost control incentives but Preferred Provider Organizations (PPOs) did not. We show that cost growth and its components cannot be understood without accounting for (i) consumers’ switching between plans, and (ii) differences in cost characteristics between new entrants and those leaving the market. New entrants are markedly less costly than those leaving (and their costs fall after their entering year), so cost growth of continuous enrollees in a plan is significantly higher than average per-member cost growth. Relatively high-cost HMO membe...
September 2016Hospital Network Competition and Adverse Selection: Evidence from the Massachusetts Health Insurance Exchange
Health insurers increasingly compete on their covered networks of medical providers. Using data from Massachusetts’ pioneer insurance exchange, I find substantial adverse selection against plans covering the most prestigious and expensive “star” hospitals. I highlight a theoretically distinct selection channel: these plans attract consumers loyal to the star hospitals and who tend to use their high-price care when sick. Using a structural model, I show that selection creates a strong incentive to exclude star hospitals but that standard policy solutions do not improve net welfare. A key reason is the connection between selection and moral hazard in star hospital use.

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