The Massachusetts Division of Health Care Finance and Policy has released a study examining trends in health expenditures statewide.  Required under state law, the report outlines spending in public, fully insured, and self-insured health plans.  The report found that private payers $15.9 billion, or 43 percent, of health expenditures statewide in 2008.  The authors determined that Medicare and Medicaid accounted for $11.6 billion and $9.4 billion, respectively.

From the report:

Private insurers and self-insured health plans collectively paid health care providers an estimated $15.9 billion, or 43 percent of estimated total health care spending, for services used by
Massachusetts residents under comprehensive coverage arrangements in 2008 (Figure B).2 Medicare accounted for $11.6 billion or 32 percent of this spending, while MassHealth accounted for $9.4 billion or 26 percent in 2008. Patterns of spending by payer reflect differences in their covered populations as well as differences in payment practices. 

Full report: Massachusetts Health Care Cost Trends: Trends in Health Expenditures (PDF | 5.67 MB)

Massachusetts Division of Health Care Finance and Policy.  (2011).  Massachusetts health care cost trends: trends in health expenditures.