The Yao (known in Vietnam as Dao) nationality (its great majority branch is also known as Mien; Traditional Chinese: 航壁, Simplified Chinese: ?壁, Pinyin: Y?o z?; Vietnamese: ng??i Dao) is a government classification for various minorities in China. They form one of the 55 ethnic minority groups officially recognized by the People's Republic of China, where they reside in the mountainous terrain of the southwest and south. They also form one of the 54 ethnic groups officially recognized by Vietnam. In the last census in 2000, they numbered 2,637,421 in China, and roughly 470,000 in Vietnam. Black Dao (pronounced ˉZaoˇ) women wear plain black trousers and black jackets decorated at the sleeves and collars with coins, embroidery and a maroon ruff. Their hair is set in a characteristic chignon held in place by a large silver frame not unlike the base of an inverted candelabrum; this sits on top of the head, wrapped in thick black cord and draped with a black scarf decorated with beads and maroon tassels.