A study published in the Archives of Internal Medicine found that 88 percent of physicians accepted new privately insured patients in 2008, down from 93 percent in 2005.  The authors cited low reimbursement rates and significant administrative burdens as possible reasons for the decline.  The study also notes that rate of acceptance declined less for Medicare beneficiaries, dropping from 96 to 93 percent between 2005 and 2008.

Bishop, Tara F. et. al. (2011). Declines in physician acceptance of Medicare and private Coverage. Archives of Internal Medicine, 171 (12): 1117 - 1119. doi:10.1001/archinternmed.2011.251. http://archinte.ama-assn.org/cgi/content/short/171/12/1117

Authors: Tara F. Bishop, Alex D. Federman and Salomeh Keyhani.