for all aspects of daily life, the central government could force obedience from problematic individuals. The central government's efforts to contain migration has been a major factor in the rapid development of the Chinese economy. Their tight check on migration into urban areas has helped prevent the emergence of a number of problems faced by many other developing countries. For example, the appearance of slums outside of urban areas due to a massive influx of individuals searching for work has not been an issue, nor have poor health conditions due to high population density. And regardless of its other imperfections, the hukou system's ability to maintain stability has contributed to China's economic rise. Human rights activists state that the hukou system has also been used to systematically deny Uyghurs and Tibetans from moving out of Xinjiang or Tibet by disallowing them from renting or buying housing in more eastern parts of China, and that any who do manage to leave are commonly forced to return through the system. History The legacy of the Chinese hukou system may be traced back to the pre-dynastic era, as early as the 21st century BC. In its early forms, the household registration system was used primarily for the purposes of taxation and conscription, as well as regulating migration. Two early models of the hukou system were the xiangsui and baojia systems. The xiangsui system, established under the Western Zhou Dynasty (circa 11th-8th centuries BC) was used as a method of organizing and categorizing urban and rural land. The function of the baojia system, propagated by Lord Shang Yang of the 4th century BC, was to create a system of accountability within groups of citizens: if one person within the group violated the strict rules in place, everyone in the group suffered. This structure was later utilized and expanded upon during the Qin Dynasty (221-207 BCE) for the purposes of taxation, population control, and conscription. According to the Examination of Hukou in Wenxian Tongkao published in 1317, there was a minister for population management during the Zhou Dynasty named Simin (), who was responsible for recording births, deaths, emigrations and immigrations. The Rites of Zhou notes that three copies of documents were kept in different places. The administrative divisions in Zhou Dynasty were a function of the distance to the state capital. The top division nearest the capital was named Dubi (), top division in