About Cannonball’s data
Cannonball reads the shelf of about 3,160 Coles, Woolworths, IGA and ALDI supermarkets in Australia every day: price, promotions, ranging and, where the chain shows it, stock, product by product and store by store. Its public figures compare chains only where they are measured the same way, and each one carries the day it is for.
What Cannonball reads
About 3,160 stores of 4 chains: Coles (about 870), Woolworths (about 1,140), IGA (about 540) and ALDI (about 610), about 128,000 product listings in all, read every day. Not every value is read at every store of every chain: Chains and coverage has the table, chain by chain. A value filled in rather than read at a store is marked as inferred, and a value we don’t know is shown as unknown, never as zero (Observed and inferred numbers).
No retailer login, supplier portal or scan data is needed. Cannonball is independent of every retailer.
Days and freshness
Every date is a Sydney day: “11 October” means the shelf as it stood that day. New figures arrive each morning, and a change can show a day after it happened (Freshness). Every public figure says the day it is for.
On special
A product is on special when the chain shows a promotion on it at one store or more that day, as the chain itself labels it. Specials are counted at Coles and Woolworths, where every store’s promotions are read the same way. IGA stores each set their own, so IGA isn’t compared with the two.
Shares of the products read
A share is of the products read at one store or more that day. That’s almost all of Coles’ list and about two thirds of Woolworths’, so a share of the whole list would undercount Woolworths. A product that wasn’t read that day is left out, never counted as not on special.
What we never compare
- Chains on stock or out-of-stocks. Stock is read at every Coles store, at some Woolworths stores, for ALDI’s Special Buys only and not at IGA, so no fair ranking of the chains exists.
- Prices between chains. No public figure says one chain is cheaper or dearer than another.
- A chain on its own, on something unflattering. Coles and Woolworths stand side by side on the same measure, or not at all.
- A brand next to bad news. Brand pages show range and specials, nothing about stock.
Rounding
Brand, category and chain pages round their counts: exact below 20, two significant figures from there (“about 250”). The data pages give exact counts and shares to one decimal place.
The figures
- Coles vs Woolworths specials this week: the share of products on special, by category, every day.
- When Coles and Woolworths specials change: the day of the week products go on special.
- Brands at Coles and Woolworths: range and specials for each grocery brand.
Questions
Which supermarket has the most out-of-stocks?
Cannonball doesn't rank Australian supermarkets on out-of-stocks, because the chains can't yet be measured the same way: stock is read at every Coles store, at some Woolworths stores, for ALDI's Special Buys only, and not at all at IGA, which lists only what each store sells. A ranking from those would compare different things.
Is Coles or Woolworths cheaper?
Cannonball doesn't publish a price comparison between the chains. It counts specials at both on the same measure; see Coles vs Woolworths specials.
Where does the data come from?
Cannonball reads the shelf of about 3,160 Coles, Woolworths, IGA and ALDI stores in Australia every day. It needs no retailer login, supplier portal or scan data, and it is independent of every retailer.
Can I quote Cannonball's figures?
Yes. Name Cannonball (cannonballdata.com), give the date the figures are for, and link the page. Each day's specials figures keep their own address, such as https://cannonballdata.com/data/coles-vs-woolworths-specials/<date>.
Journalists and researchers: get in touch for a figure we don’t publish yet.