Physician and Practice Characteristics Associated with Family Physician Panel Size

Purpose: Understanding primary care panel sizes is crucial as US policy makers and workforce planners wrestle with both primary care shortage and rising clinician burnout. We aimed to investigate physician and practice factors associated with variation in panel size. Methods: We analyzed data from the 2017 to 2023 American Board of Family Medicine (ABFM) Family Medicine Continuing Certification Questionnaire. The nationally-representative, mandatory (100% response rate) questionnaire included demographic, practice, and panel size data for family physicians (FPs). Bivariate analyses and generalized linear models with a log-linked γ distribution examined associations between panel size and physician, practice, and area characteristics. Results: 21,770 FP respondents reported estimated panel size averaging 1,933 patients/FP. On adjusted analyses, FPs in independently owned practices reported the largest panel sizes, while those in academic practices and federal clinics had the smallest panel sizes. FPs working in practices of 2 to 5 physicians had larger panel sizes than those in solo or larger group practices. FPs providing obstetric and inpatient care had smaller panel sizes than their counterparts. Working with nurse practitioners or physician assistants was associated with larger panel sizes. A greater proportion of vulnerable patients in a practice was associated with smaller panel sizes. Panel size decreased over time after adjusting for other predictors. Conclusions: Panel sizes among FPs vary significantly based on practice type and size, team composition, and scope of practice. These findings highlight the importance of considering both individual and practice-level factors in workforce planning and policy development to optimize primary care delivery and manage physician workloads effectively.