To examine whether certain patient or physician characteristics were associated with longer visit duration, we pooled visits across all 9 years of the study period. We used bivariate techniques and multiple linear regression analysis to estimate patient, practice, and physician characteristics associated with visit duration. Our primary outcome was visit duration. Covariates in the multivariate model included patient factors such as sex, new patient (yes or no), visit type (GME or other), insurance (Medicare, private insurance, or other), age (18-35, 36-49, 50-64, 65-75, or ≥76 years), and race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, or other). We also included physician factors such as whether the visit was to a general practitioner or family practitioner or to a general internist, whether the physician practiced solo or was part of a group practice, what US Census region the visit occurred in (Northeast, Midwest, South, or West), whether the metropolitan area of the visit was urban or rural, and whether the practice was physician owned or not. Finally, we included visit year as an indicator variable.