Examining the Number of Competitors and the Cost of Medicare Part D: Working Paper 2014-04

Most beneficiaries of Medicare's Part D prescription drug insurance choose among private drug plans to receive their coverage. This paper is the first to examine the relationship between the number of competing plan sponsors and the cost of Part D during the program's first five years. Over the period from 2006 to 2010, regional Part D markets contained between 16 and 22 plan sponsors offering stand-alone plans. Consistent with economic theory, we find that increases in the number of plan sponsors within a market were associated with lower bids and lower overhead and profits of plans in that