When selecting our supermarket locations, we drew on ABS data to provide a good representation of Australia, taking into account geography, population size, distance to the nearest city centre, socio-economic status, and clusters of the different supermarket chains.
The result was a list of 110 supermarkets – 32 Coles, 32 Woolworths, 26 Aldi and 20 IGA stores – in 33 locations across Australia.
In compiling our grocery list we first studied retail sales data to ensure we included items regularly purchased by average Australians. The intent was to compile a list of commonly purchased items that we could compare on price, rather than a basket that's representative of an average weekly shop.
Basket items were also selected to give good coverage of grocery categories: from beverages, biscuits, bread, cereal, confectionery, canned fish, frozen veg, pasta, chilled dairy, snacks and smallgoods, right through to kitchen wrap and household cleaning products.
The resulting grocery list consisted of 33 items, 28 of which were packaged products (including beef mince, chicken breast fillets and eggs). The remaining five items were fresh fruit and veg (apples, bananas, broccoli, carrots and potatoes), chosen for being commonly purchased and the least likely to vary in quality between locations, and were included just as an indicator. We kept the number of fresh fruit/veg items to a minimum because the quality can vary widely across stores and geography, creating too many variables for a fair price comparison.
See below for the full list of items priced.
All up we priced seven different baskets of these items:
- Leading brand basket (priced at Coles, Woolworths and IGA)
- Supermarket brand basket: Aldi
- Supermarket brand basket: Coles
- Supermarket brand basket: Woolworths
- Budget basket: Aldi
- Budget basket: Coles
- Budget basket: Woolworths
Brand and product selection
Identification of leading brands for each item was done in consultation with the Retail World Annual Report 2015, and the closest comparable supermarket brand items were selected accordingly.
We put a lot of due diligence into choosing our basket items across the leading and supermarket brands to ensure we were making fair comparisons. Where possible we tried to stick to more commoditised – or basic – items with limited differences across brands, to ensure we compared like with like. Canned tomatoes were chosen over ready-made tomato-based pasta sauce, for example, as pasta sauce recipes can vary significantly from brand to brand.
We also spent a lot of time in stores and online to ensure the item we chose had comparable, nationally distributed products across the leading and supermarket brands – that meant they needed to be similar in size, type or style, as well as appearance.
For our budget baskets we took our supermarket brand baskets and substituted items for budget versions where they were available. Smart Buy instead of Coles brand cling wrap, for example, or Homebrand rather than Woolworths Select frozen peas.
Prices collected in IGA stores were for leading brand items only. Due to availability issues, the basket we used when comparing prices between IGA and the other supermarkets was identical but consisted of 25 (of the 28) packaged leading brand items.
Data collection and analysis
CHOICE engaged with a qualified partner accredited with the Mystery Shopping Providers Association to undertake the fieldwork. Sixty-six undercover shoppers collected price data at the nominated supermarkets in March 2017 within five days between a Thursday and the following Tuesday.
For each item we provided shoppers with a photo and specified the quantity, weight or pack size to ensure they were collecting prices for the correct product. Shoppers were required to record the last two digits of the barcode as part of the validation procedure in Coles, Woolworths and IGA. Due to labelling inconsistencies, this was not possible at Aldi stores. Each shopper was required to photograph the price tag of four different items, purchase at least one item and submit a scan of the shopping docket confirming the time and location of the shop.
The data was collected via an online program that required the entry of a price in a consistent format for each item before they could complete the shop. Every shopper’s price list was validated for accuracy and completeness for quality assurance.
When comparing the 2017 prices of baskets between stores, we used the percentage difference calculation, which is the difference between the average of the two baskets.
Other considerations when shopping for groceries
Supermarkets are an enormous source of research fodder, and the focus of this piece of research was on price. But we understand that many other factors are often considered when choosing where to shop or which products to buy, including convenience, quality, supporting smaller and/or local producers and country of origin. And for some people, these other factors may be of higher priority than price.
If these issues are of interest to you, check out the following:
- We regularly review quality by comparing nutrition, performance or taste of products (including leading and supermarket brands) within individual product categories. More recent examples include cheddar cheese, toilet paper and hot cross buns. If there is a product category you'd like to see us tackle, you can request a test.
- Our supermarket investigation looked at the growth in supermarket/private label brands and its impact on the availability of smaller or more niche independent brands.
- We frequently report on the country of origin of food. Articles we've published include an investigation into where supermarket products are sourced and a review of country of origin statements on frozen fruit and veg. This year in our supermarket price survey we compared the country of origin statements on the food items in each of the baskets, to see where the products had been sourced.
- We have long campaigned to improve free range egg labelling, as the label on your carton can have any number of meanings depending on the producer. Although we're disappointed that the new national standard for free range eggs fails consumers, we're determined to provide consumers with the information they need. Download for free the latest version of our egg-finding app CluckAR, to find which eggs are genuinely free range.
The CHOICE shopping list
- Bread, white, sliced
- Chocolate, milk, block
- Milk, full fat
- Butter (A)
- Cheese, block
- Ice cream, vanilla
- Peas, frozen
- Biscuits, chocolate coated
- Chips, crinkle cut
- Jam, strawberry
- Breakfast cereal
- Coffee, instant
- Juice, orange
- Cling wrap
- Tuna, canned
- Oil, Olive
- Tomatoes, diced, canned
- Pasta, dried penne
- Flour, white, plain
- Sugar, white
- Tissues, aloe vera
- Hand wash, antibacterial
- Laundry detergent (B)
- Dishwashing liquid
- Eggs, free range]
- Chicken breast fillets, skinless
- Beef mince, premium
- Apples, Granny Smith
- Potatoes, washed
(A) A cheaper margarine/spread was substituted for butter in all three of the supermarkets' budget baskets.
(B) A cheaper laundry liquid detergent was substituted for powder detergent in all three of the supermarkets' budget baskets.
Read the results of our 2017 supermarket price survey