Building Works Tender Price Index (BWTPI) is a quarterly index compiled by the Architectural Services Department as an aid to adjust building cost data for estimating purposes. It also provides an indication of the level of tender prices for new building works undertaken by the Architectural Services Department. The BWTPI does not reflect the level of tender prices for mechanical and electrical contracts. It is computed in a similar way to that used by the Royal Institution of Chartered Surveyors' Building Cost Information Service in the United Kingdom. The value in the first quarter of 1970 is taken to be the base index value of 100, and subsequent values are expressed in index form based on the first quarter 1970 value.