, and anonymous reviewers for very helpful comments. This study was approved by UC Irvine's Institutional Review Board (HS#2013-9942). The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research. At least one co-author has disclosed a financial relationship of potential relevance for this research. Further information is available online at http://www.nber.org/papers/w21669.ack NBER working papers are circulated for discussion and comment purposes. They have not been peer-reviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

At least one co-author has disclosed a financial relationship of potential relevance for this research. Further information is available online at http://www.nber.org/papers/w21669.ack NBER working papers are circulated for discussion and comment purposes. They have not been peer-reviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

We design and implement a large-scale field experiment on age discrimination to address limitations of past research that may bias their results. One limitation is the practice of giving older and younger applicants similar experience in the job to which they are applying, to make them “otherwise comparable.” The second limitation is ignoring the likelihood of greater variation in unobserved differences among older workers owing to human capital investment. Based on evidence from over 40,000 job applications, we find robust evidence of age discrimination in hiring against older women, but considerably less evidence of age discrimination against older men.