British census tracts were first developed in the city of Oxford. The Inter-University Census Tract Committee was formed in 1955[11] and Oxford was divided into 48 tracts with an average population of 2,645 each.[12] The Registrar General, however, opted for enumeration districts containing less than 1,000 people on average, rather than adopting census tracts.[11] While tracts composed of enumeration districts were later developed, these were not extensively used.[13] Census tracts have, however, been constructed and used by British demographers.[14] The Office for National Statistics now uses enumeration districts only for the collection of data, with output areas used as the base unit in census releases.[15]