Doolittle joined MDRC in 1986, initially specializing in studies of employment and training programs for economically disadvantaged, out-of-school young people and adults. As MDRC expanded its work to include education, he focused on evaluations of elementary and secondary school reforms. At various points in his career at MDRC, he was Director of the Policy Research and Evaluation Department and the K-12 Education Policy Area and Interim Director of the Postsecondary Education Policy Area. He has served on the faculties of Harvard University’s John F. Kennedy School of Government, the Woodrow Wilson School of Public and International Affairs at Princeton University, and the Yale School of Management. Doolittle holds a law degree and a Ph.D. in economics from the University of California at Berkeley. At the end of 2020, he transitioned to consultant status and now services as Chair of MDRC’s Institutional Review Board and as a senior advisor to MDRC.