Chernew, Michael E., Lindsay M. Sabik, Amitabh Chandra, Teresa B. Gibson, and Joseph P. Newhouse. "Geographic Correlation Between Large-Firm Commercial Spending and Medicare Spending." American Journal of Managed Care 16.2 (February 2010): 131-138.
The positive correlation in utilization and lack of correlation in spending implies an inverse correlation in prices. This is consistent with evidence that the differences appear to be, at least partially, related to aspects of the market structure. If private markets are to work better to reduce cost, stronger efforts are needed to reduce provider market concentration and promote competitive pricing for healthcare services.