Although it may seem obvious that charging higher premiums for smoking (or high body-mass index, cholesterol, or blood pressure) would encourage people to modify their habits to lower their premiums, evidence that differential premiums change health-related behavior is scant. Indeed, we're unaware of any health insurance data that have convincingly demonstrated such effects....

In general, the effectiveness of outcome-based wellness incentives is uncertain, and their use raises concerns about distributional equity; nevertheless, these approaches are gaining momentum because of rising health care costs and payers' belief that incentives should work in health care as they do in other spheres. Lessons from behavioral economics could improve incentive-program design, but real-world implementation challenges may lead to substantial deviation from theoretically optimal design. Developing and testing a variety of programs between now and 2014 will generate the data needed to determine how best to use this new approach to improve health.