HCCI data on market concentration was mentioned in a Health Affairs blog post.
From the article:
“Before we even get into the merits and effects of Congress’ fix for surprise billing, it’s worth noting that the status quo is bad for networks. Most markets—particularly in urban areas—are highly concentrated, giving providers such as hospitals and specialists a great deal of market power. The Health Care Cost Institute recently found that in 2016, 72 percent of hospital markets would qualify as “highly concentrated per the Department of Justice.” This market power allows such providers to demand high in-network rates. ”
https://www.healthaffairs.org/do/10.1377/hblog20191112.220629/full/