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Two lines on a chart for Coles and Woolworths moving in a weekly up,down pattern between two prices.

Two lines on a chart for Coles and Woolworths moving in a more irregular up,down pattern between two prices.

A grid of supermarket products that are all moving in a regular up and down weekly pattern.

A grid of supermarket products that are all moving in an irregular up and down pattern.

Adam Williamson sits at his computer smiling at the camera.
Coles and Woolworths Trend creator Adam Williamson has been collecting data from Australia's two major supermarkets.(Supplied: Adam Williamson)

A big computer screen showing yellow bar chart with a finger pointing to them.
Coles and Woolworths Trends went live in the middle of the year.(Supplied: Adam Williamson)

The Coles line moves up and down, while the Woolworths line does not follow an exact up and down pattern.

Sanjoy Paul smiles at the camera in a professional headshot.
Business researcher Sanjoy Paul said high-low pricing was a known retail strategy.(Supplied: Sanjoy Paul)

A grid of products where the size corresponds to the number of products. The biggest grid is pantry.

A purple mountain that starts low at 0% and peaks between 40 and 50 per cent.

Lots of purple mountains where the peaks are different for each product, the biggest being for personal care items.

Greg Jericho smiles at the camera.
The Australia Institute's Greg Jericho said Coles and Woolworths pricing strategies were locking customers in.(ABC News: Michael Barnett)

Coles yellow sales tickets on a shelf.
The ACCC said similar price changes did not necessarily indicate collusion. (ABC News: Patrick Rocca)

A sign in Woolworths that says "1/2 Price" in the toiletries aisle.
Coles and Woolworths said they did not have visability of the other's pricing.(ABC News: Patrick Rocca)

A supermarket aisle with yellow sales tickets and a woman walking down with a trolley.
The ACCC is currently investigating supermarket prices.(ABC News: Patrick Rocca )

A banner reading 'Coles' and, in the background, the Woolworths logo.
There are calls for the ACCC to monitor supermarket prices permanently.(ABC News: Charlie McLean)

  • The data obtained for 26 May 2024 to 17 August 2024 inclusive covers a 12-week period containing an entry for every product captured by Coles and Woolworths Trends for the respective supermarket website each day. The data was scraped from each website's site-map, so products with an active URL were captured.
  • The product's price and availability was collected. Any product that was available for less than 70 days was omitted from the analysis.
  • Four extreme outliers — where the price moved more than 20 times in the given period — were omitted from the analysis.
  • Online prices are understood to be largely the same as in-store prices, with differences depending on location and perishable items. Online-only specials have been included in the analysis, which represent a very small proportion of the total products analysed.
  • Both the Coles and Woolworths data had between 2-5 days missing for various products. It was assumed the products affected were unavailable on that day.
  • Cigarettes were removed from the category analysis as there were only three products represented.
  • The recorded price change may not have happened on that exact day listed, but on a day or two earlier due to the timing of the data collection.
  • Not every line of the dataset was validated, but it was cross-checked against open-source supermarket price platform HotPrices.org for its available data. The method was validated after the fact with a manual spot check of more than 200 products across four weeks after the analysed period. The platforms Coles Trends and Woolworths Trends are also public facing and have been open to scrutiny since July.
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