This book was first published in 1995. The problem of disparities between different estimates of GDP is well known and widely discussed. Here, the authors describe a method for examining the discrepancies using a technique allocating them with reference to data reliability. The method enhances the reliability of the underlying data and leads to maximum-likelihood estimates. It is illustrated by application to the UK national accounts for the period 19201990. The book includes a full set of estimates for this period, including runs of industrial data for the period 19481990, which are longer than those available from any other source. The statistical technique allows estimates of standard errors of the data to be calculated and verified; these are presented both for data in levels and for changes in variables over 1-, 2- and 5-year periods.