Price indices on the basis of unit values: Unit value indices as proxies for price indices
AbstractIn some countries a Paasche price index based on unit values is compiled as a proxy for a true Paasche (or Laspeyres) price index on the basis of prices. This is for example the case in German foreign trade statistics. Unit values are average prices referring to a 'commodity number' (CN), that is an aggregate of (more or less homogeneous) commodities defined by a commodity classification. They are often easily available as free by-products of other statistics (foreign trade or wage statistics for example) and therefore less costly than true transaction prices of well-defined specific products as they are in general reported in price statistics. Changes in unit values between two points in time, however, do not only reflect a price movement but also changes in the quantities transacted. They are, in other words, affected by a structural component, the changing mix of commodities within CNs and therefore biased relative to genuine price indices. The focus of the paper is on explaining this bias. It is shown that amount and sign of the 'unit value bias' depends on the correlation between the change of quantities of the goods included in the CNs and their respective base period prices, while current period prices do not matter. This result is useful as it may help to define 'homogeneity' with respect to CNs and thus conditions under which unit values may be acceptable as (cost-effective) substitutes for prices. --
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Bibliographic InfoPaper provided by University of Duisburg-Essen, Faculty for Economics and Business Administration in its series IBES Diskussionsbeiträge with number 185.
Date of creation: 2010
Date of revision:
price index; unit value index; unit values; axioms; foreign trade statistics; Bortkiewicz; Drobisch;
Find related papers by JEL classification:
- C43 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods: Special Topics - - - Index Numbers and Aggregation
- C80 - Mathematical and Quantitative Methods - - Data Collection and Data Estimation Methodology; Computer Programs - - - General
- E01 - Macroeconomics and Monetary Economics - - General - - - Measurement and Data on National Income and Product Accounts and Wealth; Environmental Accounts
- F10 - International Economics - - Trade - - - General
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