Fig 1. Estimated referral probabilities stratified according to the managed care status (MC).

Fig 1 shows the estimated referral probabilities (y-axis) in relation to the patients’ age (x-axis) based on the multivariate hierarchical regression model and stratified according to the managed care status (MC). The regression model controlled for all determinants depicted in Table 2. A significant non-linear association exists between the referral probability and patients’ age, which is independent of the MC status. Panels (A) to (C) show the independent influence of different patient and PCP determinants on the referral probability (A), number of reasons for encounters, (B) sex of PCP, (C) patient load per day.