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.