According to the Office for National Statistics, at the 2001 census there were over a million black people in the United Kingdom; 1% of the total population described themselves as "Black Caribbean", 0.8% as "Black African", and 0.2% as "Black other". Britain encouraged the immigration of workers from the Caribbean after World War II; the first symbolic movement was those who came on the ship the Empire Windrush. The preferred official umbrella term is "black and minority ethnic" (BME), but sometimes the term "black" is used on its own, to express unified opposition to racism, as in the Southall Black Sisters, which started with a mainly British Asian constituency, and the National Black Police Association, which has a membership of "African, African-Caribbean and Asian origin".