Hagen was born to CEO Ragnar Hagen (1908-1969) and accountant Gerd Gamborg (born 1914) [REF].
Prior to dedicating his professional life to politics, Hagen was CEO at Tate & Lyle Norway from 1970 to 1974, and after falling out of parliament between 1977 and 1981, consultant of Finansanalyse from 1977 to 1979, and economic policy consultant in the oil industry from 1979 to 1981 [REF].