We all know the cost of groceries has gone up in Australia.

But would your shopping be cheaper in comparable countries like New Zealand, the UK or Ireland?

Now, you can see for yourself.

Researchers from Edith Cowan University have collected and compared the prices of some common supermarket staples.

Here's how Australia's duopoly performs compared to other leading supermarket brands overseas — Sainsbury's, Tesco, Pak'n'Save, Countdown and Dunnes.

Associate Professor Flavio Macau and Dr Alex Wang collected data on 44 grocery items between April and May this year.

The above table shows a sample of their findings.

They wanted to check how Australia stacks up to similar markets overseas and whether the Coles and Woolworths duopoly is to blame for high grocery prices.

How does Australia compare?

First of all, let's look at the cost of groceries in Australia.

Food prices at Coles and Woolworths rose by 9.6 per cent over the past 12 months to April.

But the price difference between the two major supermarkets is small.

Dr Macau found in a grocery trolley of 50 products, the cost of 45 products was the same at Woolworths and Coles.

The overall price difference on a $300 shop was less than a dollar.

Yet Choice found an Aldi trolley of groceries was 25 per cent cheaper.

This could mean the big supermarkets are either in a battle to the bottom on price or a cruise to the top.

"To better understand what's happening in Australia, we compared it with overseas markets," Dr Wang said.

Is there more competition overseas?

The comparison looked at the two largest supermarkets in each country, to mimic Australia's Coles-Woolworths duopoly, which has 65 per cent of the market share.

In New Zealand, there's a similar duopoly — Pak'n'Save and Countdown (New Zealand's brand for Woolworths) hold 70 per cent of the market.

In the UK, Tescos and Sainsbury's account for 42 per cent of the market.

While in Ireland, Dunnes and Tescos hold a 45 per cent share.

Dr Macau found prices varied significantly more overseas between supermarkets compared to Australia.

Which country is the winner?

To make a fair comparison Dr Macau and Dr Wang found unit prices for each grocery item and applied exchange rates to have all prices listed in Australian dollars and added up the cost of a trolley full of groceries.

The total cost of the so-called "basket" of groceries (language used by the researchers but in actual fact more like a trolley full) is the sum of all 44 grocery items tracked in the research. 

Here's the winning order on price alone:

1. UK — on top with the lowest prices, with the cost of the groceries ranging between $283—$297.
2. Ireland — next cheapest with prices ranging between $313—$345.
3. Australia — in third with the price the groceries between $324—$332.
4. New Zealand — the most expensive with a cost ranging from $342—$409.

But, that's not quite the full story. The average wages of workers are different between the countries.

Dr Macau and Dr Wang compared the prices to wages, calculating how many hours a typical person would need to work to buy the trolley load of groceries.

When adjusting for wages, Australia's grocery "basket" is the second cheapest:

1. UK
2. Australia
3. Ireland
4. New Zeland

Dr Macau said, based on median incomes, both Australian and UK shoppers spent about 13 per cent of their wages on groceries, which includes food and non-food items.

Action taken against Australia's supermarket duopoly

Coles recently posted a $1.1 billion profit for the 2023-24 financial year, up 2.1 per cent on the previous year.

While Woolworths experienced a 93 per cent drop in profit to $108 million, partly due to its operations in New Zealand.

Multiple inquiries are underway into the supermarket set-up in Australia.

Australia's competition watchdog has launched legal action against Coles and Woolworths, accusing them of increasing prices on products only to later advertise them as discounted.

Coles says it takes compliance with Australian consumer law extremely seriously and intends to defend the proceedings, while Woolworths says it will review the claims and continue to engage with the consumer watchdog.

Researchers suggest breaking up the duopoly might be 'counterproductive'

The federal Greens are calling for the supermarket duopoly to be broken up.

"Coles' $1.1 billion profit is a sick joke for the millions of Australians struggling to afford food and groceries," Greens senator Nick McKim said.

But Dr Macau said his study pointed to the need for a more nuanced approach.

"Implementing radical solutions, such as compelling supermarkets to disinvest, might have counterproductive effects, potentially increasing prices due to rising costs," he said.

He said despite the perception that supermarket profits were substantial, they were modest when examined through the context of costs and revenue.

Dr Macau compared the supermarkets' earnings before interest and taxes divided by sales for 2024.

He found Coles to be 4.8 per cent, Woolworths 4.7 per cent, Pak'n'Save was 2.6 per cent, Countdown 1.3 per cent and Tescos 7.1 per cent after a difficult year the previous year.

Dr Macau said ACCC investigations into allegations of consumer deception by Coles and Woolworths highlight that accountability was key.

"A strategy that empowers consumers with smart shopping practices and encourages strategic purchasing could offer a more immediate and effective solution."