In the 20th century, Norwegian academics have been pioneering in many social sciences, including criminology, sociology and peace and conflict studies. Prominent academics include Arne Næss, a philosopher and founder of deep ecology; Johan Galtung, the founder of peace studies; Nils Christie and Thomas Mathiesen, criminologists; Fredrik Barth, a social anthropologist; Vilhelm Aubert, Harriet Holter and Erik Grønseth, sociologists; Tove Stang Dahl, a pioneer of women's law; Stein Rokkan, a political scientist; and economists Ragnar Frisch, Trygve Haavelmo, and Finn E. Kydland.