Purpose: To describe trends in the size of radiology practices from 1990 to 2007.
Methods: Data from the American College of Radiology's 1990, 1995, 2000, and 2003 surveys of radiologists and radiation oncologists and its 2007 survey of radiologist members are compiled to describe the changing distribution of radiologists by practice size over time. All estimates are weighted to be representative of all radiologists in the United States.
Results: The fraction of radiologists in small practices (1-4 radiologists) decreased from 29% in 1990 to 22% in 2007. The fraction in medium-sized practices (5-14 radiologists) decreased from 51% in 1990 to 38% in 2007. The fraction in practices with 15 to 29 radiologists increased from 14% in 1990 to 21% in 1995 and has since remained constant. The fraction in practices with 30 or more radiologists grew from 5% in 1990 to 19% in 2007, but since 2000, growth among these practices has largely been limited to practices with 60 or more radiologists. The median radiologist was in a 7-radiologist practice in 1990. This size increased to 11 in 2000 and was the same in 2007. The size of a practice at the 90th percentile of radiologists increased from 22 in 1990 to 45 in 2007.
Conclusion: Radiology practices grew in size throughout the 1990 to 2007 period. In general, changes were more rapid in 1990 to 2000 than since. The most conspicuous growth was in practices with 30 radiologists or more. This category almost quadrupled its share of radiologists. In contrast, the share of very small practices (1-4 radiologists) declined relatively little, by only approximately one-fourth.