This is not mere theory, economists have shown. Daron Acemoglu and Joshua Linn found that as the potential market for a type of drug grows, so do the number of new drugs entering that market. Amy Finkelstein showed that policies that made the market for vaccines more favorable in the late 1980s encouraged 2.5 times more new vaccine clinical trials per year for each affected disease. And Meg Blume-Kohout and Neeraj Sood found that Medicare’s introduction of a drug benefit in 2006 was associated with increases in preclinical testing and clinical trials for drug classes most likely affected by the policy.

Health care innovation can have direct benefits for health, well-being and longevity. A study led by a Harvard economist, David Cutler, showed that life expectancy grew by almost seven years in the second half of the 20th century at a cost of only about $20,000 per year of life gained. The vast majority of gains were because of innovations in the care for high-risk, premature infants and for cardiovascular disease. These technologies are expensive, but other innovation can be cost-reducing. For instance, in the mid-1970s, new dialysis equipment halved treatment time, saving labor costs.

Even with those undeniable improvements, there are questions about the nature of American innovation. Work by Mr. Garthwaite, along with David Dranove and Manuel Hermosilla, showed that although Medicare’s drug benefit spurred drug innovation, there was little evidence that it led to “breakthrough” treatments.

And although high prices do serve as incentive for innovation, other work by Mr. Garthwaite and colleagues suggests that under certain circumstances drug makers can charge more than the value of the innovation.

The high cost of health care, an enormous burden on American consumers, isn’t necessarily a unique feature of our mix of private health insurance and public programs. In principle, we could spend just as much, or more, under any other configuration of health care coverage, including a single-payer program. We spend a great deal right now through the Medicare program — often held out as a model for universal single-payer.

Despite the fact that traditional Medicare is an entirely public insurance program, there’s an enormous market for innovative types of care for older Americans. That’s because we are willing to spend a lot for it, not because of what kind of entity is doing the spending (government vs. private insurers).