After several years working at an accounting firm, Fisher was hired by the National Resource Planning Board in 1939. He was promoted to become an economist for the U.S. Department of State in 1942. He was drafted into the U.S. Army in 1943 to serve in World War II. Fisher returned to the United States after the war ended and earned a Ph.D. from Harvard University. He was then hired by the Council of Economic Advisors and, after furthering his education at George Washington University, became the senior economist at this organization in 1951. In 1953, Fisher joined the efforts of a non-profit think tank known as Resources for the Future, Inc.