Practice composition and sex differences in physician income: observational study

OBJECTIVE To assess whether differences in income between male and female physicians vary according to the sex composition of physician practices. DESIGN Retrospective observational study. SETTING US national survey of physician salaries, 2014-18. PARTICIPANTS 18 802 physicians from 9848 group practices (categorized according to proportion of male physicians <= 50%, >50-75%, >75-90%, and >90%). MAIN OUTCOME MEASURES Sex differences in physician income in relation to the sex composition of physician practices after multivariable adjustment for physician specialty, years of experience, hours worked, measures of clinical workload, practice type, and geography. RESULTS Among 11 490 non-surgical specialists, the absolute adjusted sex difference in annual income (men versus women) was $36 604 (29 pound 663; (sic)32 621) (95% confidence interval $24 903 to $48 306; 11.7% relative difference) for practices with 50% or less of male physicians compared with $91 669 ($56 587 to $126 571; 19.9% relative difference) for practices with at least 90% of male physicians (P=0.03 for difference). Similar findings were observed among surgical specialists (n=3483), with absolute adjusted sex difference in annual income of $46 503 ($42 198 to $135 205; 10.2% relative difference) for practices with 50% or less of male physicians compared with $149 460 ($86 040 to $212 880; 26.9% relative difference) for practices with at least 90% of male physicians (P=0.06 for difference). Among primary care physicians (n=3829), sex differences in income were not related to the proportion of male physicians in a practice. CONCLUSIONS Among both non-surgical and surgical specialists, sex differences in income were largest in practices with the highest proportion of male physicians, even after detailed adjustment for factors that might explain sex differences in income.