to compete with Japanese and German wares. Labor strikes happened with such frequency as to almost paralyze the country's infrastructure. Following the Winter of Discontent, Margaret Thatcher was elected prime minister in 1979 with the purpose of implementing extreme economic reforms. In Eastern Europe, Soviet-style command economies began showing signs of stagnation, in which successes were persistently dogged by setbacks. The oil shock increased East European, particularly Soviet, exports, but a growing inability to increase agricultural output caused growing concern to the governments of the COMECON block, and a growing dependence on food imported from democratic nations. On the other hand, export-driven economic development in Asia, especially by the Four Asian Tigers (Hong Kong, South Korea, Singapore, and Taiwan), resulted in rapid economic transformation and industrialization. Their abundance of cheap labor, combined with educational and other policy reforms, set the foundation for development in the region during the 1970s and beyond. Oil crisis Economically, the 1970s were marked by the energy crisis which peaked in 1973 and 1979 (see 1973 oil crisis and 1979 oil crisis). After the first oil shock in 1973, gasoline was rationed in many countries. Europe particularly depended on the Middle East for oil; the United States was also affected even though it had its own oil reserves. Many European countries introduced car-free days and weekends. In the United States, customers with a license plate ending in an odd number were only allowed to buy gasoline on odd-numbered days, while even-numbered plate-holders could only purchase gasoline on even-numbered days. The realization that oil reserves were not endless and technological development was not sustainable without potentially harming the environment ended the belief in limitless progress that had existed since the 19th century. As a result, ecological awareness rose substantially, which had a major effect on the economy. Science and technology Science The 1970s witnessed an explosion in the understanding of solid-state physics, driven by the development of the integrated circuit, and the laser. Stephen Hawking developed his theories of black holes and the boundary-condition of the universe at this period with his theory called Hawking radiation. The biological sciences greatly advanced, with molecular biology, bacteriology, virology, and genetics achieving their modern forms in this decade. Biodiversity became a cause of major concern as habitat destruction, and Stephen Jay Gould's theory of punctuated equilibrium revolutionized evolutionary thought. Space exploration As the 1960s ended, the United States had made