As Medicare beneficiaries double over the next 30 years, controlling per enrollee spending growth becomes increasingly more important. Cost containment, therefore, is a major feature of most Medicare reform discussions. When assessing private and public approaches, a careful comparison of spending growth between Medicare and private insurers can shed light on which sector is better able to control per enrollee spending in the long run. This research note discusses some recent relevant studies and the important data limitations of this type of analysis.