Brass was born in Edinburgh, where he went to school at the Royal High School and earned a Master's degree in mathematics and natural philosophy from the University of Edinburgh in 1947; during the Second World War he served in the Royal Navy Scientific Service.
[1][2][3] Brass's career as a demographer began in 1948 when he worked as a statistician, then as deputy director, for the East African Statistical Department in Nairobi, which collected and analysed data on Kenya, Uganda, Tanganyika and Zanzibar.
[1] Beginning with his work in East Africa, Brass developed what he called indirect estimation, techniques for deriving statistics on fertility, mortality and population growth from imperfect and incomplete data, including devising and working from simple questions such as the number of living children and living parents a respondent has.
[1][2][3][5] He also worked on population modelling and on British demography, for example analysing the role of female employment[2] and predicting that the high birth rate amongst immigrants in the 1970s would not continue.
[3] 1978: The Population Association of America gave him the C. Mindel Sheps Award for contributions to mathematical and applied demography.