Waves of mass migrations from Hong Kong villagers exercised their right of abode in the United Kingdom and left for Europe. In 1967, a series of large-scale riots erupted in Hong Kong, causing social instability. These events led some of the richer Hong Kong residents to move abroad. Emigration took place to countries in Southeast Asia, South Africa or South American countries. This wave did not come to a rest until the mid-1970s. On the 19th of December 1984, the People's Republic of China and the United Kingdom signed the "Sino-British Joint Declaration", validated the 1997 transfer of sovereignty over Hong Kong to China. The declaration prompted
British nationality law and Hong Kong on or after 1983 to a parent settled in Hong Kong are BDTCs. The law also stated that British Citizens or BDTCs by descent could not automatically pass on British nationality to a child born outside the United Kingdom or the dependent territories concerned unless a parent acquired citizenship otherwise than by descent. Negotiation concerning the future of Hong Kong started in the late 1970s between Britain and China. With the signing of the Sino-British Joint Declaration on 19 December 1984, the future of Hong Kong was set, with China to assume sovereignty of the entire territory of Hong Kong