The weekly shop for Toowoomba mother Tammie Irons, like many Australians, has been getting increasingly expensive.

She said feeding her teenagers was a struggle and she often spent more than $300 a week on groceries.

“They eat a lot more than younger children … I also have two coeliac boys, so the price of groceries is becoming increasingly more expensive for us,” Ms Irons said.

To help cut down the cost of shopping, Ms Irons uses the Woolworths loyalty program.

“By the time I get to Christmas, I’ve got around $150 or so off my shop, which I really appreciate,” she said.

But critics have raised concerns the massive amount of data being collected is helping further expand the power the two supermarket giants have in Australia.

What data do the supermarkets collect?

Coles and Woolworths operate the Flybuys and Everyday Rewards loyalty schemes respectively.

The schemes collect data from customers, including “what, how, when and where you buy from us”, according to the Woolworths privacy policy.

The data is used in a number of ways, including personalised marketing and for insights on customer behaviour.

Coles said the data could also be used to “protect our lawful interests and facilitate purchases or our businesses”, while Woolworths cited “investigations in cases of fraud or data security risks” as a possible use.

Data control

Queensland Fruit and Vegetables Growers (QFVG) said the data held by the two big supermarkets gave them immense power over producers.

CEO Rachel Chambers said the data, combined with the use of supply agreements with growers, allowed supermarkets to control the supply and demand of fresh produce.

The agreements, as outlined in submissions to the Senate inquiry on supermarket prices from Coles and Woolworths, see growers and supermarkets negotiate each week on the prices of fruit and vegetables.

The prices are affected by factors including market availability and the volumes needed, with each party given the right to reduce costs or adjust the amount of produce needed on any given week.

In its submission to the Senate inquiry, the QFVG said the supermarkets’ control of data gave them the ability to negotiate lower prices with growers and thus create an unfair market.

“They understand exactly what the consumer buys, basically, on a day-to-day basis, their data is so intense,” Ms Chambers said.

Ms Chambers said she believed many people were unaware their data was contributing to such a power imbalance.

“The data asymmetry, the power imbalance, sits within the data.”

The QFVG has called for a greater discussion about the collection of data and how imbalances can be addressed.

It suggested periodic price data be provided to an independent body to act as a watchdog over the market.

In statements provided to the ABC, Woolworths said it was standard practice for businesses to look at previous sales to help predict future demand and that it was investing millions of dollars in advertising to promote Australian produce.

Coles said it used data to inform its ordering requirements to ensure produce was available to customers at any given time and at affordable prices.

Doubling down

Coles and Woolworths are both doubling down on big data – Coles earlier this year signed a deal with US defence company Palantir to “optimise its workforce”, while Woolworths purchased data company Quantium in 2021 for $223 million.

“It’s part of a broader move that both Australian chains are making to move towards a sort of more data-driven, high-data-collection kind of way of doing business,” University of Queensland research fellow Luke Munn said.