The researchers will explore how private fee-for-service (PFFS) plans and beneficiary choices are affected by Medicare payment policy. PFFS plans cover services from any Medicare-qualified provider and pay physicians by fee-for-service. The researchers will measure the effects of payment changes on PFFS plan decisions regarding market entry, benefit design, and premiums and then analyze the effects of changes in benefits and premiums on enrollment. They will address the following research questions: (1) how would plan availability be affected if payment rates were reduced; (2) how would premiums and benefits be affected by changes in payment rates; and (3) how does the value to beneficiaries of the PFFS option compare to its cost to the taxpayers? The objective of the proposed project is to inform policymakers about the costs and benefits of paying private Medicare health insurance plans.