Over the last decade or so, companies have been looking to "do well by doing good" with their health- care provisions: to cut the amount they spend on health insurance, and lose to absenteeism, by encouraging employees to take better care of themselves. A recent study by Rand found that in 2012, about half of employers with at least 50 employees — and more than 90 percent of those with more than 50,000 — had one of these programs in place.

They range from discounted gym memberships and wellness workshops to ultimatums; the Cleveland Clinic monitors its employees' blood levels for various conditions, and it won't have sugared soda on its campuses. Moreover, the legendary institution refuses to hire smokers, and it forced those already working for them to quit — smoking, or the job. There are also programs that focus on the behavior of people with expensive chronic conditions such as diabetes or asthma. Usually these involve a nurse regularly reaching out to these patients, cajoling them into taking their medication and monitoring their symptoms, and possibly catching potential problems early.

Such programs should reduce a company's health-care spending. But until now, we haven't had data showing whether they actually do.