The Dream of Wiping Out Polio Might Need a Rethink

Well Done! - If, at the number of people immunized, marginal social benefit of immunization equals its marginal cost, and the outcome is 15 cases of polio per quarter, the outcome is efficient.

Correct! - The marginal social cost of polio immunization increases, and the marginal social benefit of polio immunization decreases as more and more people are immunized. The people remaining to be immunized tend to live in the African countries with poor health-care systems, which creates a large gap between marginal social cost and marginal social benefit.