The AMA has gathered first-of-its-kind data on pharmacy benefit managers and its analysis finds a widespread high degree of market concentration in local markets across the U.S. where PBMs provide services to commercial health insurers.

…

At the national level, the analysis found that a handful of PBMs have a large collective market share for the three PBM services most used by insurers:

• The 10 largest PBMs had a collective share of 97%.
• The four largest PBMs had a collective share of roughly 66%.
• Six PBMs are used exclusively by one insurer or a set of Blue Cross Blue Shield affiliates.

From my latest at the AMA. The whole shebang.