Special Economic Zones（经济特区) were the first cities in China to be opened to the outside world, established in 1979. Deng Xiaoping believed that a new system must be fully tested before it could be extended to the whole country. After the reform and opening up, Deng introduced foreign investment in only four cities - Zhuhai, Shenzhen, Shantou and Xiamen - because he feared that opening up to capitalist countries would undermine the socialist system.
Background
In November 1977, Deng Xiaoping came to Guangdong Province for inspection. At that time, many residents in Guangdong were risking their lives to smuggle themselves across the border to the more affluent Hong Kong. Deng Xiaoping believed the key reason was that the current policy was wrong. Stopping residents from defecting to Hong Kong could not rely solely on the troops.
In 1978, after examining the economic situation in Hong Kong and Macau, the Communist Party of China thought that it could take into account the experience of Hong Kong and Macau and implement new policies to attract investment and absorb management experience in the areas adjacent to Hong Kong and Macau.