He returned to Statistics Norway in 1923 and received his doctorate in 1925 with a dissertation on the sex proportion at birth and infant mortality.
Wedervang became lecturer at the University of Oslo in 1925 and was appointed professor of economics and statistics in June 1926.
Wedervang belonged firmly to the school of empirically oriented Norwegian economists in the tradition of Anton Martin Schweigaard.
His work in the 1920s comprised an estimate of national income in Norway and some articles on trade problems.
His tenure was only interrupted by the German occupation of Norway when he was removed from his position due to patriotic attitude, and incarcerated in a concentration camp.