How do communities improve the health of their populations? For the past century, we have not been required to think deeply about the question because health status steadily improved. Life expectancy increased by 30 years in prosperous countries between 1900 and 2000. But now the question is emerging as one of the most important we face.

The rate of “natural” improvement in health status appears to be slowing, and decline is not unthinkable if the sharp rise in the prevalence of chronic conditions such as obesity and type 2 diabetes continues unabated. Research identifying the nonmedical determinants of health has flourished in recent decades. The correlations are well understood, but the causes of health disparities and the extent to which they can be mitigated remain debatable. How do societies come to take population health improvement seriously? One potential pathway is incentives.

Improving health care is hard; improving population health is even harder, as the articles in this issue of Preventing Chronic Disease discuss. Decades of analysis and experimentation have confirmed the following:

1. Targets can be useful but also distracting and unintentionally destructive to the population health agenda.
2. Little evidence supports the proposition that population health can be improved with resources freed up by making health care more effective and efficient.
3. Pay-for-performance is fraught with difficulties in practice, among them methodologic problems and moral hazard.
4. Health status variability is inevitable, but even people who are born with identical health status will have diverse outcomes over the life course because of circumstances and choices.
5. Experiences in other sectors reveal the mixed and sometimes unforeseeable effect of incentives.
6. Producing effective and durable reward systems is difficult in health care, and more difficult still in population health.