3 'HE significant and varied roles which measures of price changes have come to play in the analysis and administration of the modern economy require that they be adapted to playing those parts. That is, of course, a maxim for those who prepare the price measures. But what is argued here is addressed equally to those who use price measures. One might say with justice that such an appraisal is made necessary by the fact that interest in price measures is no longer limited to the specialist. Price facts now provide part of the background information, and even formulas, which enter into public and private decisions. Millions of dollars in private commodity or wage contracts turn on movements of published price series or indexes. Congressional hearings abound with price movement comparisons such as between farm and retail prices or the latter and wages. Equally important, however, are questions about economists' practice, for they now use price measures for such diverse purposes as putting dollar figures in real terms, comparing movements of prices among vertical steps in the industrial structure, or studying the timing of the response of different types of industries to dynamic influences. Altogether price measures are used for a variety of purposes to indicate what goes on in a variety of markets in response to a variety of dynamic influences. Yet whether the reference is to a price series or to a composite index number, a single type of measure, conceptually, is all that is ordinarily available. This is the reported price for a specified item frequently used to represent a product line, or else an index number for a set of such prices, that is, the weighted average of the reported prices for a representative, fixed bill of carefully specified goods. It is true that some widely-used indexes such as that of hourly earnings and that of prices paid by farmers depart from this standard, but to that extent they are considered to be defective.' Whether or not it conforms to this objec-