⁶Gray (2006) reports estimates that total HMO enrollment peaked in 1999 and then declined, although not quite as quickly as in the data in table 2. It should be remembered that studies are based on surveys; that surveys of course vary; that some data is reported in multiple stages (Gray reports in personal conversation that his data was preliminary), and that survey responses in all cases are likely to reflect respondent uncertainties due to enrollees’ and even employer purchasers’ difficulty in figuring out what was a PPO and what was an IPA or another loose form of HMO. In any event, by 1999 the PPO form was emerging triumphant. [Return to Text]