The Measles and Free Riders.

This article takes up a game-theoretic perspective on California's recently passed bill (SB 277) that closes all nonmedical exemptions for school-mandated vaccination. Such a perspective characterizes parental decisions to vaccinate their children as a collective action problem and reveals the presence of an incentive to free ride-to enjoy the benefits of others' efforts to vaccinate their children without vaccinating one's own. This article defends California's legislation as a reasonable means of overcoming the free rider problem and of ensuring that the burdens of vaccination are shared equally.