UK Online Shelf-Price Index

Posted online shelf prices, not prices paid. Not a CPI and not a government statistic. Independent: not affiliated with, endorsed by or sponsored by Tesco, Sainsbury's, Asda or Aldi. This version is vintage 2026-W44, revision 1: the second change week of the current series (base 2026-W42 = 100). The all-products headline was 99.7238 (-0.2409% week on week) and food and soft drinks 99.8139 (-0.2055%), from 74,335 products matched in both weeks, with all four retailers in the headline. The four-week change starts at 2026-W46. Changes from this vintage (earlier vintages are unchanged and stay as published): the headline and retailer rows carry four counts, `entered` (products in this week's snapshot that were not in last week's), `left` (the reverse), `relinked` (products matched by their barcode after a change of identifier, not counted as entered or left) and `missingPackSize` (matched products whose pack size is shown in only one of the two weeks); the counts describe the weekly snapshots, not the retailers' ranges. A product relaunched under a new identifier with the same barcode is matched within its retailer; Aldi's online data carries no barcodes, so this never applies to Aldi. A pack size missing in one week is still treated as unknown, not carried forward. No index was produced for 2026-W41; the closed first series (base 2026-W39) is a separate record, and levels in the two series cannot be compared. `matched` counts products found in both weeks before any are left out, and `matchedShare` can be above 1 when products move into a class between the weeks. The index follows the posted online shelf prices of the same products at Tesco, Sainsbury's, Asda and Aldi in the UK from one week to the next, matched on each retailer's own product id in weekly snapshots of the retailers' websites. Within each retailer and product class the weekly change is a Jevons index (equal product weights); the all-products headline weights the four retailers equally. There are no spending weights. Currency: GBP. The files hold index numbers and counts only (level, week-on-week and four-week change, matched counts and share, status, and from 2026-W44 the weekly counts), keyed by retailer and product class: no product names, prices, product ids, images or URLs. Method and data dictionary: https://data.yappman.com/shelf-price-index/method/ . Each version of this record is one dated vintage; published vintages are never revised (a correction would be a new, marked revision). Product-level shelf prices on request (Tesco, Sainsbury's, Asda and Aldi) are available from a pay-per-event Actor on the Apify Store, charged to the Apify account that runs it: https://apify.com/yappman/uk-supermarket-price-scraper