Under certain conditions, index numbers may do very useful service as an aid to investigation into the history and statistics of prices; for the extension of the theory of the nature and value of money they are unfortunately not very important

Under certain conditions, index numbers may do very useful service as an aid to investigation into the history and statistics of prices; for the extension of the theory of the nature and value of money they are unfortunately not very important (Ludwig von Mises, The Theory of Money and Credit)