Michael Cannon at Cato writes:
By 2017, in most markets, a single hospital system had more than a 50 percent market share of discharges. In 2016, markets for specialist physicians exhibited what federal antitrust authorities consider a high degree of concentration in 65 percent of metropolitan areas. Markets for primary‐care physicians exhibited high concentration in 39 percent of metropolitan areas…. In 2016, 57 percent of health insurance markets exhibited high concentration; in 2018, 75 percent did.
Why that’s bad: the economics literature finds that concentration increases prices and reduces quality.