What is a counterfactual baseline?

Baselines are built from the patterns in a store's own history — trend, seasonality, day-of-week structure — often disciplined by control stores or market data that reveal what similar locations did over the same window. The measured impact is then the gap between actual results and that expectation, not the gap between actual results and an arbitrary comparison period.

The difference is not academic. A price increase followed by a 2% traffic decline looks damaging against last month — and looks like a win if the market around the brand declined 4% over the same weeks. Same data, opposite conclusion; the baseline is what decides which is true.