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Data editing and scanner data

Data editing and scanner data. I. Léonard, G. Varlet and P. Sillard Insee. The French Consumer Price Index (CPI) (1/5). Laspeyres yearly chained index fixed basket of products during a year comparison between the prices in the current month and those of last December

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Data editing and scanner data

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  1. Data editing and scanner data I. Léonard, G. Varlet and P. SillardInsee UNECE - Work session on statistical data editing

  2. The French Consumer Price Index (CPI) (1/5) • Laspeyres yearly chained index • fixed basket of products during a year • comparison between the prices in the current month and those of last December • replacements for products not sold anymore in a shop during the year after a quality-adjustment UNECE – Work session on statistical data editing

  3. The French Consumer Price Index (CPI) (2/5) • each month 120,000 prices collected in 27,000 shops by 160 price collectors • additional collection done centrally for some sectors (electricity, public transports, mobile phones, …) • information provided by companies UNECE – Work session on statistical data editing

  4. The French Consumer Price Index (CPI) (3/5) The price collectors choose : • the shops • in a sample of 96 cities representative of the French household consumption • in different types of shops to be consistent with the distribution channels • the products • inside varieties UNECE – Work session on statistical data editing

  5. The French Consumer Price Index (CPI) (4/5) Variety : • small groups of products • defined in a very detailed manner • the set of varieties of a product family is representative of the price dynamics of the whole family UNECE – Work session on statistical data editing

  6. The French Consumer Price Index (CPI) (5/5) • A two-step computation • micro-indices at variety and city level using adequate price index formulae to deal with possible substitutions made by the consumers • Laspeyres aggregation of the macro-indices UNECE – Work session on statistical data editing

  7. The scanner data project (1/5) • European Article Number (EAN) • internationally managed by GS1 for manufactured goods UNECE – Work session on statistical data editing

  8. recorded by retailers in centralized databases used for stock management and market research NSI interested to compute CPI for several years could be used to develop estimates of average prices and to make spatial comparisons of price levels The scanner data project (2/5) UNECE – Work session on statistical data editing

  9. The scanner data project (3/5) Aims • to increase the quality of disaggregated indices with a basket of products much larger than the present one • to select a non biased sample of products with adequate random sample design • to estimate the accuracy of the indices • to include a broader range of products • to apply new statistical methods without changing the basic concepts UNECE – Work session on statistical data editing

  10. The scanner data project (4/5) An experiment • since November 2012 • until at least December 2014 • involving 4 major companies • under voluntary agreements UNECE – Work session on statistical data editing

  11. The scanner data project (5/5) Two indexes in addition to the scanner data to describe shops and products UNECE – Work session on statistical data editing

  12. Data editing in the computationof the current French CPI (1/4) • two stages, same principles • principles : computation of two confidence intervals of price variations • based on the whole previous year • by large groups of products UNECE – Work session on statistical data editing

  13. Data editing in the computationof the current French CPI (2/4) UNECE – Work session on statistical data editing

  14. Data editing in the computationof the current French CPI (3/4) • automatic confirmation of all price variations inside level 1 CI • instant check in the shop by the price collector of price variations inside level 2 CI and outside level 1 CI  confirmation or correction UNECE – Work session on statistical data editing

  15. Data editing in the computationof the current French CPI (4/4) For price variations outside level 2 CI : • instant check in the shop by the price collector  confirmation or correction + explanation of the price variation (stage 1) • check of the explanation in offices  possible reject of the price (stage 2) UNECE – Work session on statistical data editing

  16. Data editing in the scanner data project (1/3) • same principle of price change confidence intervals • no possible check in shops • The accuracy of the CI must be improved The large volume of the database makes it possible UNECE – Work session on statistical data editing

  17. Data editing in the scanner data project (2/3) Computation of CI : • at the variety level • more frequently (monthly or quarterly) • by variety and large area • for a specific product on a recent period • based on the sample or the whole database UNECE – Work session on statistical data editing

  18. Data editing in the scanner data project (3/3) Balance between : • the improvement of statistical processes thanks to the large volume of data vs. • the performances of computers An common issue to all the processes of the project UNECE – Work session on statistical data editing

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