Which valued-based price when patients are heterogeneous?

We use a simple model to study the static and dynamic efficiency of alternative regulation regimes for the reimbursement of medical innovations when responses to a new treatment (effectiveness) are heterogeneous across the eligible population. When the rational behavior of profit-maximizing firms is taken into account, only average value-based prices can ensure both static and dynamic efficiency, but they imply higher expenditure and lower consumer surplus. Ignoring dynamic efficiency, if patients' responses are sufficiently homogeneous, marginal value-based prices may dominate from the payer's perspective. We also present a refinement of average value-based prices that could reverse this result. Overall, the cost of ensuring static and dynamic efficiency is increasing in the degree of heterogeneity. A real-world example is used to illustrate these results.