Understanding the status of BNOs
The BNO status is one of the major classes of British nationality under British nationality law. Holders of this nationality are Commonwealth citizens, but not British citizens. They are not automatically granted right of abode anywhere, including the United Kingdom and Hong Kong through their British national (overseas) status.
History of BNO
The creation of the class of BNO was a response to the question of the future prospect for Hong Kong in the 1980s. Therefore the nationality was tailor-made for the Hong Kong residents with British dependent territories citizen status by virtue of their connection with Hong Kong.
The nationality also served to retain an appropriate relationship with the United Kingdom after the transfer of sovereignty of Hong Kong to the People’s Republic of China in 1997. From 1 July 1987 to 1997, around 3.4 million of British dependent territories citizens of Hong Kong (mainly ethnic Chinese), successfully gained BNO status by registration. Hong Kong's British dependent territories citizenship then ceased to exist after 30 June 1997.
As of 2007, 3.44 million of Hong Kong residents had the status as BNO, although only 800,000 of them held a valid BNO passport. As the BNO nationality cannot be gained anymore, the number of them slowly decreases and will eventually disappear.
For a more detailed breakdown on BNO visit WhatPassport