Background article, updated October 23, 2026. Our earlier Canadian collection has stored prices dated December 11, 2025 through March 21, 2026, with gaps. The current collection began March 22, 2026. See collection dates and gaps.
A sale price is useful only when you know what it applies to. Keep the product, package, store, dates and offer conditions together. A low price on a different pack, or a price reserved for members, may answer a different question.
Read the offer before comparing it
Check whether the advertised price applies to one item or requires a larger purchase. Look for membership requirements and an end date. Keep those conditions with the price instead of treating every advertised offer as a simple discount.
The same product can have different offers at different chains. Compare the products and dates you actually have, rather than assuming a promotion applies everywhere a chain operates.
Check the usual price
A lower price by itself does not confirm a sale. When the retailer supplies a regular price and sale label, keep both. If either is missing, leave that uncertainty in the result.
Calculate a discount only when the regular price and sale price refer to the same product and purchase conditions. Check the package size and unit price before comparing discounts between products.
Follow the dates
Keep the day the price was recorded separate from any stated offer dates. If a later record is missing, you cannot tell from the price file alone whether the sale ended on that day.
Sale labels in earlier data need the checks described in the collection method. A price change and a confirmed sale label are different pieces of evidence.
Use price data for price questions
Recorded prices can show when a retailer listed a sale and how that price compared with its earlier records. They do not establish sales volume, profit margin or the cause of a competitor's decision.
Download the sample data to inspect its sale fields, or get a free API key.