China, officially the People's Republic of China (PRC), is a country in East Asia and the world's most populous country, with a population of around 1.404 billion. Covering approximately 9,600,000 square kilometers (3,700,000 sq mi), it is the third- or fourth-largest country by total area, depending on the source consulted. Governed by the Communist Party of China, the state exercises jurisdiction over 22 provinces, five autonomous regions, and four direct-controlled municipalities of Beijing, the capital city, Tianjin, Shanghai, the largest city, and Chongqing), and the special administrative regions of Hong Kong and Macau. China emerged as one of the world's earliest civilizations, in the fertile basin of the Yellow River in the North China Plain. For millennia, China's political system was based on hereditary monarchies, or dynasties, beginning with the semi-legendary Xia dynasty in 21st century BCE. Since then, China has expanded, fractured, and re-unified numerous times. China's economy has been one of the world's fastest-growing with annual growth rates consistently above 6 percent since 1978. As of 2016, it is the world's second-largest economy by nominal GDP and largest by purchasing power parity (PPP). China is also the world's largest exporter and second-largest importer of goods. China is a recognized nuclear weapons state and has the world's largest standing army and second-largest defense budget. The PRC is a permanent member of the United Nations Security Council as it replaced the ROC in 1971, as well as an active global partner of ASEAN Plus mechanism. China is also a leading member of numerous formal and informal multilateral organizations, including the Shanghai Cooperation Organization (SCO), WTO, APEC, BRICS, the BCIM, and the G20. China is a great power and a major regional power within Asia, and has been characterized as a potential superpower.