Prof. Collier was the head of the economics department of the John F. Kennedy Institute. He also was the institute director from 2011 to 2017. He retired from the Freie Universität Berlin in July 2018 and has taught at Bard College Berlin during the following four years, 2018-2022. His current research focuses on the development of the undergraduate and graduate curricula in the United States, 1870-1970. His blog Economics in the Rear-View Mirror is a respected digital repository of  valuable archival transcriptions for the international community of the historians of economics.