A new Federal Trade Commission study found that primary care is far less concentrated than many physician specialties, with just 18% of primary care ZIP codes classified as highly concentrated.
Published March 11, the study uses claims data from six major insurers across 15 states from 2015 to 2020. The FTC estimates the data covers about 82% of the commercial insurance market in those states and includes roughly 51 million to 53 million commercially insured beneficiaries, making it one of the broadest recent looks at physician practice structure and patient choice.
The study uses the Herfindahl-Hirschman Index, or HHI, a standard measure of market concentration and competition.
Here are 10 more things to know:
1. By comparison, 42% of OB-GYN ZIP codes, 49% of general surgery ZIP codes, 51% of orthopedic surgery ZIP codes and 58% of cardiology ZIP codes were classified as highly concentrated.
2. In 2018, the median HHI for primary care was 1,058, compared with 1,623 for OB-GYN, 1,819 for orthopedic surgery and 2,016 for cardiology, highlighting the narrower range of choices patients often face in specialty care.
3. Some specialties were highly concentrated in nearly every ZIP code in the sample, including critical care, geriatric medicine, hematology/oncology, interventional cardiology, radiation oncology and rheumatology, each of which exceeded the 1,800 HHI threshold in 100% of ZIP codes.
4. Rural and nonmetro areas were consistently more concentrated than metro areas. In primary care, the share of ZIP codes above the high-concentration threshold rose from 14% in metro counties to 38% in nonmetro counties adjacent to metro areas and 44% in non-adjacent nonmetro counties.
5. The metro-rural divide was even more pronounced in cardiology, where 52% of metro ZIP codes were highly concentrated, compared with 93% of nonmetro-adjacent ZIP codes and 95% of non-adjacent nonmetro ZIP codes.
6. Multispecialty practices accounted for a large share of physician care, including 66% of primary care, 76% of cardiology, 71% of gastroenterology and 64% of orthopedic surgery.
7. Health system affiliation was also common, though it varied widely by specialty. It accounted for 34% of primary care, 43% of general surgery and 46% of cardiology, compared with 12% of allergy/immunology and 10% of ophthalmology.
8. The report also found sharp geographic differences. Nearly all OB-GYN care in Florida occurred in highly concentrated ZIP codes, while much of Texas was not highly concentrated for OB-GYN services.
9. The Midwest stood out for health system alignment, with roughly half of primary care in Illinois, Indiana, Missouri and Ohio delivered by health system-affiliated physicians. In much of Texas, that share was below 25%, depending on the market.
10. The report concludes that physician market structure varies widely by specialty and geography, meaning patient choice, multispecialty practice use and health system affiliation can look very different from one service line or region to another.
