Mongolia's economic development under the communist government can be divided into three periods: 1921–1939; 1940–1960; and 1961 to the present. During the first period, which the People's Republic called the stage of "general democratic transformation," the economy remained primarily agrarian and underdeveloped. After an abortive attempt to collectivize herders, livestock remained in private hands. The state began to develop industry based on processing of animal husbandry products and crop raising on state farms. Transportation, communications, domestic and foreign trade, and banking and finance were nationalized with Soviet assistance; they were placed under the control of Mongolian state and cooperative organizations or Mongolian-Soviet joint-stock companies. Ulaanbaatar became the nation's industrial center.