How much should you discount on Black Friday?

As little as gets attention. The right number is whatever is competitive in your category and no deeper — and for many stores the right answer is a bundle rather than a percentage.

Why the answer is what it is

Work out the discount at which contribution per order goes negative and stay well clear of it. Stores that lose money in November do so because they set the discount by looking at competitors instead of at their own margin.

What this looks like in practice

Discounting into a crowd where everybody is discounting wins volume and loses margin. The stores that do well have a reason to be chosen that is not the price.

Traffic spikes break the things that were nearly broken already — usually image weight and a checkout step nobody tested under load.

The customers won in that week are worth almost nothing unless something brings them back in January.

Where a mobile app comes into it

This is the one week where owning a notification channel pays for the year — reaching last year’s buyers costs nothing per message.