§ Mr. SpellerTo ask the Chancellor of the Exchequer when his Department first used the Laspeyres-based formula for the retail prices index.
§ Mr. Maples[holding answer 15 October 1990]: The retail prices index and its predecessor, the cost of living index, have always been based on the Laspeyres formula. These figures were first compiled in 1914. Since 1962 a variant known as the "chain Laspeyres" formula has been used, whereby the weights, while remaining fixed for 12 months at a time, are brought up to date at the beginning of each calendar year.