Black Friday: which deals are real

How we judge a real deal

• We compare with prices we saw ourselves. We read every shop's price every night and keep every change. A deal here is today's price against the price we recorded for most of the 30 days before it changed.
• A shop's “was” price is not enough. It is often a list price nobody paid, or a price charged for a day before the sale. We show it when the shop gives one, but we never rank by it.
• A one-day price rise does not count. The usual price is the one that held longest, so a price pushed up for a night and then “cut” is not a deal here.
• We need a week of our own prices. A product we have watched for under 7 days is not shown, however big its drop looks.
• Only fresh drops. A price that fell more than 30 days ago is just the price now. Drops under 5% are left out.
• Cheaper next door? If another shop sells the same model for less, the card says so.