He was born in Bergen as a son of jurist and economist Einar Einarsen (1868–1913) and Emilie Wiborg (1868–1953).
He was hired at the Royal Frederick University in 1932, and worked there until 1936 while also being a teacher at Oslo Commerce School from 1934 to 1938.
degree in 1939 with a doctoral dissertation titled Reinvestment cycles and their manifestation in the Norwegian shipping industry.
[3] During the occupation of Norway by Nazi Germany he was imprisoned in Grini concentration camp on 29 July 1942, and held there until the war's end.
In 1947, he was appointed Professor of Economics at the Faculty of Law, University of Oslo, where he also served as dean until 1963.