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A Divisia index is a theoretical construct to create index number series for continuous-time data on prices and quantities of goods exchanged. It is designed to incorporate quantity and price changes over time from subcomponents which are measured in different units -- e.g. labor hours and equipment investment and materials purchases -- and to summarize these in a time series which summarizes the changes in quantities and/or prices. The resulting index number series is unitless, like other index numbers.〔Charles R. Hulten, 2008. "Divisia index" ''The New Palgrave Dictionary of Economics'', 2nd Edition. (Abstract ).〕 In practice, economic data are not measured in continuous time so when a series is said to be a Divisia index, it usually means the series follows a procedure that makes a close analogue in discrete time periods, usually the Törnqvist index procedure or the Fisher Ideal Index procedures.〔Diewert, W.E. 1993. (The early history of price index research ). Chapter 2 of ''Essays in Index Number Theory, Volume I'', W.E. Diewert and A.O. Nakamura, editors. Elsevier Science Publishers, B.V.〕 == Uses == Divisia-type indices are used in these contexts for example: * Multifactor productivity calculations use quantity indexes which incorporate changes in the expenditure share and overall quality of the underlying goods, and are then multiplied by prices. A Divisia index of all measured outputs can be divided by a Divisia index of all measured inputs to get an estimate of the productivity change that occurred apart from the changes in inputs. * Aggregation of different monetary pools, e.g. cash and credit card borrowing and different currencies. Here the pools of various monetary aggregates are treated as a quantities, and the prices are usually taken as fixed, but their ''weights'' vary -- for example, the Bank of England has an index of the money stock that is available for transactions. The index weights the various money pools by the likelihood they will be used in transactions in the near run -- physical cash and checking accounts are ready to be spent, whereas long term bonds which are not ready to be spent. The interest rate received on the various money pools is a measure of the weight; pounds in cash count more than pounds in bonds. Movement of money from one form to another affects the index whereas it would not affect a simple sum of the money stock; thus the index is more useful to track the money ready-to-transact than a sum would be.〔(Divisia money supply index ) at moneyterms.co.uk〕 The U.S. Federal Reserve Bank of St. Louis computes similar Divisia monetary aggregate indexes.〔(Monetary Services Index ) at Federal Reserve Bank of St. Louis Economic Research pages〕 * Some price indexes incorporate changes in the quantity, expenditure share, and quality on various underlying goods as well as the changes in prices for them, although the term ''Divisia index'' is not often used in the official descriptions of consumer price indexes, producer price indexes, or personal consumption indexes. Various price indexes use the Törnqvist, Fisher-Ideal, or other procedures which produce close approximations to a Divisia index. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Divisia index」の詳細全文を読む スポンサード リンク
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