Growth marketing
Attribution and last click
The rules for who gets credit for a purchase. Last click gives all of it to the final click.
Definition
Attribution is how you split the credit for a sale between the channels the customer passed through. Last click gives the whole purchase to the final click before checkout. First click gives everything to the first one. Data-driven attribution tries to split the credit based on patterns in the data.
Last click is popular because it is simple and can be counted in Google Analytics. The problem is that it favours the channels at the bottom of the funnel. Discount code sites, brand search and retargeting catch customers someone else has already convinced. The podcast that sparked interest three weeks ago gets nothing.
Every attribution model is an agreement about how to count. None of them measures what caused the purchase. Use attribution to steer day to day within a channel, and incrementality tests or MMM to decide how much money each channel should get.