From about this time, North Korea encountered increasing economic difficulties. South Korea became an economic powerhouse fueled by Japanese and American investment, military aid, and internal economic development, while North Korea stagnated and then declined in the 1980s. The practical effect of "Juche" was to cut the country off from virtually all foreign trade in order to make it entirely self-reliant. The economic reforms of Deng Xiaoping in China from 1979 onward meant that trade with the moribund economy of North Korea held decreasing interest for China. The Revolutions of 1989 in Eastern Europe and the Soviet Union, from 1989–1992, completed North Korea's virtual isolation. These events led to mounting economic difficulties because Kim refused to issue any economic or political reforms.