ABSTRACT
Cost information is recorded and collected over a period of time. During this period of time, building costs, market conditions and inflation will change for a variety of reasons. The collected data therefore, if they are to be of any use to the construction industry, must be converted to a current date or appropriate future timescale. This conversion process is normally achieved both in theory and in practice by means of index numbers. These index numbers, of which there are many different types, are used in comparing price, production, employment or population changes etc. over a certain period of time. An index number will measure the change that has occurred from one period to another.
