The GAO has issued a report on the methodology CMS uses to calculate a risk adjustment for Medicare Advantage (MA) plans, updating an analysis in provided in January 2012. The GAO previously reported that differences in diagnostic coding between MA plans and Medicare FFS resulted in inaccurately-high MA risk scores and excessive payments to MA plans. While CMS made an adjustment for coding differences in 2010, the GAO concluded that the adjustments were insufficient. Based on an analysis of two years of data available since the GAO completed its analysis for the January 2012 report, the GAO found that the cumulative impact of coding differences on risk scores increased from 2010 through 2012, and that CMS's adjustment to risk scores to account for diagnostic coding differences was too low. The GAO estimates that as a result, at least $3.2 billion in excess payments were made to MA plans over three years. The GAO continues to recommend that CMS update its methodology to more accurately account for differences in diagnostic coding between MA plans and Medicare FFS.