NBER Publications by Leila Agha

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Working Papers and Chapters

January 2015The Local Influence of Pioneer Investigators on Technology Adoption: Evidence from New Cancer Drugs
with David Molitor: w20878
Local opinion leaders may play a key role in easing information frictions associated with technology adoption. This paper analyzes the influence of physician investigators who lead pivotal clinical trials for new cancer drugs. By comparing diffusion patterns across many drugs, we separate correlated regional demand for new technology from information spillovers. Using original data on clinical trial study authors for 21 new cancer drugs along with Medicare claims data from 1998-2008, we find that patients in the lead investigator’s region are initially 36% more likely to receive the new drug, but utilization converges within four years. We further demonstrate that “superstar” physicians, identified by trial role or citation history, have substantially broader influence than less prominent ...
March 2014Negative Tests and the Efficiency of Medical Care: What Determines Heterogeneity in Imaging Behavior?
with Jason Abaluck, Christopher Kabrhel, Ali Raja, Arjun Venkatesh: w19956
We develop a model of the efficiency of medical testing based on the frequency of negative CT scans for pulmonary embolism. The model is estimated using a 20% sample of Medicare claims from 2000-2009. We document enormous heterogeneity in testing conditional on patient population. Less experienced physicians and those practicing in high spending areas test more low-risk patients. Assessing the efficiency of current practices requires calibration assumptions regarding the costs of testing, the benefits of treatment and the likelihood of false positives. While we cannot tell whether any particular testing decision was mistaken in the context of our model, we find that collectively-given these additional calibration assumptions-there are systematic differences between doctor testing practices...

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