Another study found that hospital competition in the N.H.S. decreased heart attack mortality, and several studies of Medicare also found that hospital competition results in lower rates of mortality from heart attacks and pneumonia.

Another piece of evidence in the competition-quality connection comes from other types of health care providers, including doctors. Recently, investigators from the Federal Trade Commission examined what happens when cardiologists team up into larger groups. The study, published in Health Services Research, focused on the health care outcomes of about two million Medicare beneficiaries who had been treated for hypertension, for a cardiac ailment or for a heart attack from 2005 to 2012.

The study found that when cardiology markets are more concentrated, these kinds of patients are more likely to have heart attacks, visit the emergency department, be readmitted to the hospital or die. These effects of market concentration are large.

To illustrate, consider a cardiology market with five practices in which one becomes more dominant — going from just below a 40 percent market share to a 60 percent market share (with the rest of the market split equally across the other four practices). The study found that the chance of having a heart attack would go up 5 to 7 percent as the largest cardiology practice became more dominant. The chance of visiting the emergency department, being readmitted to the hospital or dying would go up similarly.

The study also found that greater market concentration led to higher spending. And a different study of family doctors in England found that quality and patient satisfaction increased with competition.

For many goods and services, Americans are comfortable with the idea that competition leads to lower prices and better quality. But we often think of health care as different — that it somehow shouldn’t be “market based.”

What the research shows, though, is that there are lots of ways markets can function, with more or less government involvement. Even when the government is highly involved, as is the case with the British National Health Service or American Medicare, competition is a valuable tool that can drive health care toward greater value.