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Notes on scanner data & price collection in the CPI

Notes on scanner data & price collection in the CPI. Muhanad Sammar muhanad.sammar@scb.se Statistics Sweden. Swedish price collection in (the) field. Outlet sample Product sample Price collection Manually by price collectors Collection Period 3 weeks. Findings - CPI. Missing prices

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Notes on scanner data & price collection in the CPI

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  1. Notes on scanner data & price collection in the CPI Muhanad Sammar muhanad.sammar@scb.se Statistics Sweden

  2. Swedish price collection in (the) field • Outlet sample • Product sample • Price collection • Manually by price collectors • Collection Period • 3 weeks

  3. Findings- CPI • Missing prices • Time-consuming • Monotonically for price collectors

  4. Eurostats regulations - Commission regulation (EC) No 2602/2000 • “(3) Prices used in the HICP should be purchaser prices actually paid by households to purchase individual goods and services in monetary transactions, including any taxes less subsidies on the products, after reductions for discounts for bulk or off-peak purchases from standard prices or charges…”

  5. National Accounts • In the National accounts the transaction prices should be registered • Scanner data measures transaction prices • Better basis than manually collected prices for offered products

  6. Scanner data and EAN-barcode • Identifies uniquely an article, package or service • The EAN-number is international • Article Info - supplier, brand, width, depth, weight, labeling, etc

  7. Scanner data • EAN-code - not fruit & vegetables, meat & fish • Three deliveries each month • Variables • Turnover per store and EAN-code • Number of packages sold • Price (=Turnover/Number of packages sold)

  8. Four ways to use scanner data • Replace manually collected prices with scanner data • As auxiliary information • Compute index from a census based on all products • For auditing and quality control

  9. The risks of using scanner data • Deposits for beverages • Package sizes • Delivery problems • Missing values • Small volumes • Significant price increase

  10. A pilot study - Scanner Data (SD) and Manually Collected Prices (MCP) in comparison Matching categories All (49 600 products) SD and MCP. Equal prices 75 SD and MCP. Unequal prices 11 SD, but not MCP 2 Not SD and not MCP 2 MCP, but not SD 10

  11. A pilot study - Monthly price index 2009 for most of the everyday commodities Month MCP Difference S.E.* index SD-MCP January 100.24 – 0.09 0.10 February 100.73 – 0.14 0.11 March 101.02 – 0.14 0.10 April 100.94 – 0.17 0.14 May 101.14 – 0.17 0.16 June 101.67 – 0.11 0.20 July 102.11 – 0.12 0.18 August 102.12 – 0.13 0.19 September 102.35 – 0.18 0.16 October 102.54 – 0.17 0.15 November 102.68 – 0.22 0.17 * Standard error of MCP (manually collected prices) index

  12. Auditing in one selected outlet- price discrepancies for 20 of the products • Prices were erratic for 15 of the products • For 3 products the store had not updated the shelf price with the latest price information • In 2 cases, unclear descriptions of the products

  13. Decisions to make • Minimize sources of error • Improved education of price collectors • Increase the number of products • Increase the number of outlets • Average price; a week or a three-week period • Transaction price • Substitution effect

  14. Concluding remarks • Today's method is not optimal • Scanner data is compatible with EU’s regulatory framework • Scanner data allows adequate price data • In the long run; may be more cost-effective • As part of quality assurance, Statistics Sweden will continue to engage and develop routines that minimize price collector errors • CPI is an important measure and must be computed on accurate and reliable prices

  15. THANK YOU FOR YOUR ATTENTION

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