The impact of health insurance expansion on physician treatment choice: Medicare Part D and physician prescribing.

We test the effect of the introduction of Medicare Part D on physician prescribing behavior by using data on physician visits from the National Ambulatory Medical Care Survey (NAMCS) 2002-2004 and 2006-2009 for patients aged 60-69. We use regression discontinuity designs to estimate the effect of part D around the age of 65 before and after 2006 and then compare the discrete jump in outcomes at age 65 before and after Part D. We find a 32% increase in the number of prescription drugs prescribed or continued per visit and a 46% increase in the number of generic drugs prescribed or continued for the elderly after the introduction of Medicare Part D.