Forecasting on British election night 1997

An account is given of methods used to predict the outcome of the 1997 gene ral election from early declared results, for use by the British Broadcasti ng Corporation (BBC) in its election night television and radio coverage. P articular features of the 1997 election include extensive changes to consti tuency boundaries, simultaneous local elections in many districts and stron g tactical voting. A new technique is developed, designed to eliminate syst ematic sources of bias such as differential refusal, for incorporating prio r information from the BBC's exit poll. The sequence of forecasts generated on election night is displayed, with commentary.