Ignoring the skepticism of his comrades, Chairman Mao introduced the Hundred Flowers Campaign of 1956-57 encouraging intellectuals and elites from the old era to share their thoughts freely with the slogan, "Let a hundred flowers bloom, let a hundred school of thoughts contend." Mao thought that his revolution had already transformed Chinese society for good. The result was an outburst of ideas deemed unacceptable by the CCP and above all, Mao himself, which fueled his distrust of intellectuals. Mao responded with the Cultural Revolution, which saw the intelligentsia being sent to the countryside for manual labor. Post-secondary education was almost completely abolished in mainland China. There existed only 48,000 university students in China in 1970, including 4,260 in the natural sciences and 90 in the social sciences, 23,000 technical school students in 1969, and 15,000 teachers in training in 1969. Data on post-graduate students was not available, presumably because there were no such students. China had a population of around 830 million in 1970.