Impact of Medicare Advantage Prescription Drug Plan Star Ratings on Enrollment before and after Implementation of Quality-Related Bonus Payments in 2012

Objective: Since 2007, the Centers for Medicare and Medicaid Services have published 5-star quality rating measures to aid consumers in choosing Medicare Advantage Prescription Drug Plans (MAPDs). We examined the impact of these star ratings on Medicare Advantage Prescription Drug (MAPD) enrollment before and after 2012, when star ratings became tied to bonus payments for MAPDs that could be used to improve plan benefits and/or reduce premiums in the subsequent year. Methods: A longitudinal design and multivariable hybrid models were used to assess whether star ratings had a direct impact on concurrent year MAPD contract enrollment (by influencing beneficiary choice) and/or an indirect impact on subsequent year MAPD contract enrollment (because ratings were linked to bonus payments). The main analysis was based on contract-year level data from 2009–2015. We compared effects of star ratings in the pre-bonus payment period (2009–2011) and post-bonus payment period (2012–2015). Extensive sensitivity analyses varied the analytic techniques, unit of analysis, and sample inclusion criteria. Similar analyses were conducted separately using stand-alone PDP contract-year data; since PDPs were not eligible for bonus payments, they served as an external comparison group. Result: The main analysis included 3,866 MAPD contract-years. A change of star rating had no statistically significant effect on concurrent year enrollment in any of the pre-, post-, or pre-post combined periods. On the other hand, star rating increase was associated with a statistically significant increase in the subsequent year enrollment (a 1-star increase associated with +11,337 enrollees, p