Position-Based Attribution

Position-based attribution, also called U-shaped, gives most of the credit to the first and last touchpoints and a smaller share to the ones in between. The common convention is 40 percent to the first, 40 percent to the last, and the remaining 20 percent split across the middle. The reasoning is that discovery and the final push are usually the two moments marketers can act on most clearly, while the middle is supporting work. In a path with a content click, three emails, and a branded search, the content click and the branded search each get 40 percent, and the emails share 20 percent. Some tools let you change the weights, for example 30-30-40 or 50-0-50, which is a reminder that the shape comes from a human choice rather than from data.

The calculation depends on position, not on content. Take the ordered list of touchpoints, give the first and last their fixed percentages, and divide the rest evenly. With two touches, the split is 50 and 50 under this convention. With one touch, that touch takes everything. The weights are a convention, not a measurement. Nothing about your customers' behavior produces 40, 40, and 20, and a different business with a different path could justify 30, 30, 40 just as easily. That is why the model is called a rule-based model rather than a learned one. The U shape reflects a marketing story: someone finds you, others nurture, someone closes. Many real paths follow it, and many do not.

Check where you can still use it. Google announced that, starting in June 2023, it would stop letting advertisers pick position-based for new conversion actions and, starting in September 2023, would switch conversion actions still using it to data-driven attribution, with last click as the alternative. GA4 removed position-based, first click, linear, and time decay in November 2023, leaving data-driven, paid and organic last click, and Google paid channels last click. If you want U-shaped credit, you will need a separate analytics tool or a spreadsheet of exported paths. Meta's own reports will not provide it, since they use click and view windows. Where the path has only two touches, the model gives 50-50, and where it has one, that touch takes everything, so on short paths it behaves very much like first or last click.

The main mistake is treating the 40-40-20 split as an estimate of reality. It is a rule you chose, so the answers it gives reflect the rule. A second mistake is using it where it cannot discriminate: in short paths, first and last are the same touch or neighbors, and the model collapses into last click. A third is applying it to businesses where the middle matters most, such as long B2B sales with many meetings and demos, where giving the middle only 20 percent undervalues the work that moves a deal along. B2B teams sometimes use a W-shaped variant that adds a third peak at lead creation, which fits sales cycles where the key milestone is the form fill.

Use it to compare how much value your channels get at the beginning and end. Pull path data, assign position-based credit, and rank channels. A channel that ranks high under position-based but low under last click is a good opener. This week, pick your two strongest opener channels and your two strongest closers, and confirm that your budget split reflects both roles. If all your spend sits on closers, test shifting a small share to openers for a month and watch total conversions rather than channel-level credit. Whatever shape you pick, state it in the report. A channel's number means little unless the reader knows the weights behind it. If your tool lets you change the weights, try a second shape such as 30-30-40 and see whether your channel ranking changes. If it does not, the conclusion is robust.