CMS Pub. 100-16, ch. 7, § 100

Because CMS calibrates the CMS-HCC model using FFS data, the relative factors reflect

the FFS pattern of coding. CMS adjusts for the trend in the rate of increase of diagnosis

codes submitted by FFS providers with the application of a normalization factor that is

updated annually and that reduces risk scores with the goal that the average remains 1.0

in each payment year. Because MA coding patterns differ from those in FFS, MA risk

scores increase more quickly and are, therefore, higher than they would be if MA plans

coded in the same manner as FFS providers.

Beginning in 2010, CMS instituted a separate adjustment to the Part C risk scores to

account for differential coding patterns between MA and FFS. The adjustment for 2010

of 3.41% was based on our estimate of how much lower plans’ 2010 risk scores would

have been if the disease scores (the portion of the risk score attributable to diagnostic

coding) for MA enrollees who stayed in an MA plan during the period 2007 to 2010

(“MA stayers”) had grown at the same rate as FFS beneficiaries’ risk scores during this

period. In calculating the adjustment for MA coding differences, CMS removed the

impact of differences in rising risk scores that are attributed to enrollment into and

disenrollment out of MA plans, aging and other demographic changes, and adjusted for

age and sex effects on disease coding changes. For a description of the coding

adjustment for 2011-2013 please see the 2010 Rate Announcement.