In the early 1990s, North Korea began to experience a famine, labelled as the "'Great Famine"'. At the same time the Soviet Union was going through serious economic and social changes as well as suffering a stagnating economy. The Soviets, who had supplied the DPRK with food amongst other things since the late 1940s, began to demand the North Koreans to pay them back; money that the DPRK did not posses. The Soviet Union collapsed in 1991 and food aid stopped almost immediately. Kim Il Sung's centrally planned economic system, where the government plans the economic output in advance, proved to be too inflexible to avoid the economic disaster. On the 8th of July 1994, Kim Il Sung had a heart attack and died shortly afterwards, leaving his country severely bankrupt, malnourished and isolated.