▁theory . ▁Cart el ▁theory ▁remained ▁for ▁dec ades ▁the ▁product , ▁above ▁all , ▁of ▁Central ▁European ▁econom ists ▁of ▁German ▁tongue . ▁That ▁approach ▁was ▁well - int ention ed ▁to ▁the ▁entrepr ene ur ial ▁cart els ▁and ▁in ▁this ▁respect ▁was ▁functional ist ▁and ▁institution al ist . ▁It ▁had ▁its ▁origin ▁in ▁the ▁historical ▁school ▁of ▁econom ics . ▁The ▁classic ▁cart el ▁theory ▁itself ▁went ▁through ▁three ▁stages ▁of ▁development : ▁▁ ▁an ▁early ▁one , ▁partly ▁na ive , ▁in ▁which ▁the ▁" histor ical ▁school ▁of ▁econom ics " ▁strongly ▁domin ated ▁( G ust av ▁von ▁Sch m ol ler , ▁Karl ▁Bü cher , ▁Lu jo ▁Br ent ano ), ▁ ▁a ▁middle ▁one , ▁which ▁was ▁character ized ▁by ▁the ▁introduction ▁of ▁more ▁economic ▁theory ▁( es pecially ▁Robert ▁L ief mann ) ▁and ▁ ▁a ▁late ▁one ▁that ▁was ▁influenced ▁by ▁the ▁entry ▁into ▁the ▁organized ▁economy ▁of ▁the ▁German ▁Third ▁Reich ▁following ▁the ▁de pression ▁of ▁ 1 9 2 9 - 1 9 3 3 ▁( see , ▁for ▁example , ▁Hein z ▁M üll ens ief en ). ▁ ▁The ▁theory ▁variants ▁of ▁the ▁non - G erman ▁countries ▁ ▁Out side ▁of ▁the ▁German ▁speaking ▁countries , ▁there ▁were ▁more ▁or ▁less ▁similar ▁theories ▁of ▁economic ▁organization . ▁These ▁variants ▁existed ▁until ▁the ▁ 1 9 2 0 s ▁( in ▁Italy ▁until ▁after ▁ 1 9 4 5 ). ▁However , ▁they ▁operated ▁with ▁different ▁basic