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Copayments and the evidence-base paradox

When is evidence merely opinion? The evidence-base paradox is particularly relevant to the GP copayment

The proposed introduction by the Australian Government of a copayment for visits to general practitioners has received much attention. In academic journals and op-ed pages, evidence is cited that supposedly shows that the copayment is a “bad idea”.1 However, is the evidence cited relevant to this particular policy of a copayment of $5 to $7?

The RAND Health Insurance Experiment

From 1971 to 1982, the RAND Health Insurance Experiment (HIE) in the United States randomly allocated families to health insurance plans with zero, 25%, 50% or 95% copayments.2 The study found that “Cost sharing in general had no adverse effects on participant health”. This finding might support a copayment. However, the study also provides evidence against copayments by emphasising the finding that “The poorest and sickest 6 percent of the sample at the start of the experiment had better outcomes under the free plan for 4 of the 30 conditions measured”.

Participants in the RAND HIE were also grouped by the maximum percentage of their income that they were expected to contribute. Thus, even the poorest in the RAND study could be charged copayments ranging from 5%–15% of their gross income, capped at up to US$4000 per year…