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.

We design and implement a large-scale resume correspondence study to address limitations of existing field experiments testing for age discrimination that may bias their results. One limitation that may bias results is giving older and younger applicants similar experience to make them “otherwise comparable.” A second limitation is that greater unobserved differences in human capital investment of older applicants may bias the results against finding age discrimination. On the basis of over 40,000 job applications, we find robust evidence of age discrimination in hiring against older women, especially those near retirement age, but considerably less evidence of age discrimination against men.