Nurse retention and turnover were widely acknowledged as key concerns of health sector employers in the 1980s. Turnover costs can also be a significant burden in terms of the direct and indirect use of resources. The measurement of staff flows is difficult in the National Health Service (NHS), In particular, the lack of reliable and consistent information on the turnover and wastage of the nursing workforce is a continuing problem. Official data on nurse turnover and wastage are now collected via two main processes. These are: data provided by individual NHS trusts as part of the annual National Balance Sheet exercise; and data collected by the Office of Manpower Economics as part of the Nurses and Professionals Allied to Medicine Review Body. Manpower Survey coverage of which was extended to include joiners and leavers' data in 1996. Identifying and implementing effective retention policies has again assumed a more prominent position on trust management agendas.