“…However, other studies have shown that much of the increase simply reflects a shift of patients from public sites (e.g., public health departments and community health clinics) to private physicians' offices (Long, Settle, and Stuart 1986;Wade 1992;Cohen and Cunningham 1993;Baker and Royalty 1997;Gruber, Adams, and Newhouse 1997). Studies also have found that higher Medicaid enrollment levels independently increase the extent of physicians' participation in Medicaid (Held and Holahan 1985;Mitchell 1991;Adams 1994;Perloff, Kletke, and Neckerman 1986). Furthermore, at least one study found a significant negative effect of administrative inefficiency on physician participation; Perloff, Kletke, and Neckerman (1986) found that physicians who experienced delays in payment were more likely to limit the extent of their participation.…”