This article assessed Medicaid physician fees between 2003 and 2008.  On average, fees increased 15.1 percent which was below the rate of general inflation and resulted in a reduction in real fees.  Medicaid fees closed a small portion of their gap relative to Medicare fees, resulting from increases in primary care and obstetrics. 

Zuckerman, S., A. F. Williams, et al. (2009). Trends in Medicaid physician fees, 2003-2008. Health Affairs, 28(3), w510-9. DOI: 10.1377/hlthaff.28.3.w510 http://content.healthaffairs.org/cgi/content/abstract/28/3/w510 

Authors: Stephen Zuckerman, Aimee F. Williams, Karen E. Stockley