The 5% Sample Survey of Building Society Mortgage Completions (BSM) has been in existence since 1965. The Archive holds data from 1974. Monthly returns, giving detailed information on a nominal 5% sample of all mortgage completions, have been submitted on a voluntary basis by most building societies to the Department of Environment who process the data on a quarterly basis. The survey results have served as the offical source of statistics on the owner-occupied housing market, providing a wealth of information on mortgage advances, dwelling prices and the characteristics of borrowers and properties. An increased share of the mortgage market being accounted for by other lenders and a widening range of mortgage products during the 1980s have necessitated change, leading to the BSM being succeeded by the Survey of Mortgage Lenders (SML) in 1992 (see GN: 33254). An important consideration for users of the data is that the SML figures allow continuity with the BSM survey results to be maintained for a reasonable period.