Proportion of physicians in large group practices continued to grow in 2009-11.

Payers and advocates for improved health care quality are raising expectations for greater care coordination and accountability for care delivery, and physician groups may be responding by becoming larger. We used Medicare claims from the period 2009-11, merged with information from the Medicare provider enrollment database, to measure whether physician group sizes have been increasing over time and in association with physician characteristics. All US physicians serving Medicare fee-for-service patients in any practice setting were included. The percentage of physicians in groups of more than fifty increased from 30.9 percent in 2009 to 35.6 percent in 2011. This shift occurred across all specialty categories, both sexes, and all age groups, although it was more prominent among physicians under age forty than those age sixty or older. The movement of physicians into groups is not a new phenomenon, but our data suggest that the groups are larger than surveys have previously indicated. Questions for future studies include whether there are significant cost savings or quality improvements associated with increased practice size.