Share of Medicare-enrolled specialists in groups with five or fewer of their specialty, by specialty in 2019 and 2024
Published Jul 2026 · CMS Doctors and Clinicians group rosters and Part B provider types📋 CiteSee the data →
Share of Medicare-enrolled specialists in groups with five or fewer of their specialty · 2019 and 2024
Specialties are ordered by how far the share fell. A hollow dot is 2019 and a filled dot is 2024. Each clinician is counted once, in the group with the most clinicians of their specialty on its roster that year. A specialty is listed when it has at least 5,000 rostered clinicians in both years and a rostered count that changed by no more than 25%, whether or not it has a page of its own.
The share fell in 14 of 14 specialties; Neurology fell most, from 27% to 17%.
Reading the rows. Each row is one specialty. The share is the part of its Medicare-enrolled clinicians whose largest group has five or fewer clinicians of that specialty.
Ownership. Rosters cannot see ownership. A practice owned by a larger company that keeps its own Medicare billing number still counts here as a small group, so a small change does not mean a specialty stayed independent.
A record of group size, not a verdict on whether larger groups are better or worse for patients, prices, or clinicians.
What this is
The share of Medicare-enrolled clinicians in groups with five or fewer clinicians of their own specialty in 2019 and 2024, for each specialty with at least 5,000 rostered clinicians in both years.
What it is not
Not a count of acquisitions or mergers, not ownership or employment, and not who bills what. A roster records enrollment, not activity, and cannot show why a group grew.
› How this is counted
Each clinician's specialty is their most frequent Part B provider type across 2020 to 2024, so the 2019 base counts only clinicians who billed in 2020 or later, and clinicians who billed too little Part B to carry a label are not counted. A specialty is listed when it has at least 5,000 rostered clinicians in 2019 and 2024 and its rostered count changed by no more than 25%. Years after 2024 are not included because they are not on the same basis. Each clinician is counted once a year, in the group with the most clinicians of their specialty, and a group that re-registers can appear as a new group. Medicare's 2019 roster snapshot lists fewer clinicians than later years' do, so part of the change since 2019 may reflect a fuller list rather than a shift in group size.