Source for appendectomy, bariatric surgery, women's health, and maternity care:  Individual states ( AZ, CA, FL, IA, MA, MD, ME, NJ, NV, NY, OR, PA, TX, UT, VA, WA, and WI )
for years 2004 - 2006.

Source for all other procedures: Centers for Medicare and Medicaid Services for years 2005 - 2007.