Caution in Generalizing Part D Results to Medicare Population

In the August 9/23, 2010, issue, Millett and colleagues^1(p1327) wrote,

Mean out-of-pocket annual expenditures on all medications decreased by 32% . . . from $1011 to $691, in the year after Medicare Part D was implemented compared with the year before in all Medicare beneficiaries participating in the M[edical] E[xpenditure] P[anel] S[urvey].