GuideMeasurement and attribution
Attribution
Definition
The rule that decides which marketing touchpoint gets the credit for a sale when several came before it. Choosing the rule is choosing what the channel reports will say.
How it works
Last-click gives the sale to the final click before the purchase. First-touch gives it to the earliest. Linear splits it evenly across every touchpoint, and data-driven hands the split to a model, usually the platform’s own, on reasoning you cannot inspect. Run all four over the same week of sales and you get four different channel reports from identical customer behaviour; nothing changed but the rule. None of the four measures whether a touchpoint caused its sale. Each is a convention for distributing credit, so pick one rule and hold it: a changed rule looks exactly like a changed result.
What to watch for
When a channel’s numbers break trend, check whether the attribution rule or its settings changed in the same period; a report that improves when the rule changes is reporting the rule. A data-driven split nobody in the room can explain is a model’s opinion, and when the model belongs to the platform that also sells the ads, it is the platform itself that has decided how the credit is split. Your agency’s last-click report and your GA4 view will disagree about the same month while both stay faithful to their own rule, so decide in advance which report settles arguments.
The question you ask
“Has the attribution rule changed at any point in the period this chart covers?”