Today, MedPAC and the Medicaid and CHIP Payment and Access Commission (MACPAC) jointly released a data book: Beneficiaries Dually Eligible for Medicare and Medicaid. This is the second edition of this book, updated with 2010 data and new displays of 2007-2010 trends in the dually eligible population’s composition, service use, and spending.

If you missed the Commission meeting last week, you might have missed this piece of analysis. In 2012, about 28% of all Medicare beneficiaries (who have Part A and Part B) were enrolled in private Medicare Advantage (MA) plans. Recently, there has been a widely reported claim in the policy community that half of all new Medicare beneficiaries are now joining MA. The story sort of works like this: in 2012, the total number of beneficiaries in Medicare grew by two million, while the number of beneficiaries in MA grew by 1 million. These facts are true, but despite how it might sound, this does not mean that half of all new beneficiaries chose MA.