Tibet has the smallest population and is the most sparsely populated in the world. According to the latest census, the population of Tibet is 2.63 million; 92.2 percent of the population, Tibetans.
The average population density stands at 2.03 people per square km. In Tibet, population distribution is uneven, with the majority of residents living in the southern and eastern parts. The middle reaches of the Yarlung Zangbo River and the valleys of its main tributaries---Lhasa and Nyangqu Rivers---are the most densely populated areas, with more than 10 people per square km on average. The Lhasa Plain, the plains at the middle and lower reaches of the Nyangqu River and the Zetang Plain have about 50 residents per square km, and there are more than 100 people per square km in the vicinity of the Chengguan District in Lhasa. The next most densely populated areas are the upstream section on the middle reaches of the Yarlung Zangbo River, upper reaches of the Lhasa River and the northeastern part of the Hengduanshan mountainous area in east Tibet, where there are three to 10 people per square km. Of these areas, Lhaze, the Sagya Plain, the Nyang River Valley near Nyingchi and the Lancangjiang River Valley near Chamdo are more densely populated. Ngari in west Tibet and the western part of Nagqu in north Tibet are the most sparsely inhabited, and one can often make a 50-km journey without seeing any human habitation. The northern part of the Changtang Grassland is even regarded as "no man's land".
There are many reasons that affect the population density in Tibet, including historical and social factors and the development level of the productive forces; besides, the most important reason is the natural environment, the elevation in particu1ar.
Han people began to move to Tibet during the Qing Dynasty and some of them have been assimilated into the Tibetan ethnicity. Today, most Han people living in Tibet are technicians, workers and teachers from other parts of China.