What Attribution Is Actually Trying to Solve
Attribution is the attempt to assign credit for a conversion to the marketing touchpoints that influenced it. That sounds simple. It is not. A typical B2C purchase touches five to eight marketing surfaces over weeks. A B2B purchase touches dozens over months. Every model for assigning credit is a simplification that emphasizes some touches and dismisses others — and every model gets parts of the picture wrong.
The mature relationship with attribution is to stop looking for a single source of truth and start running a portfolio of measurement approaches, each appropriate for a different decision. Tactical optimization runs on platform-native attribution. Channel-level budget decisions run on data-driven multi-touch models. Strategic budget allocation runs on marketing mix modeling and incrementality testing. None of these are the truth. Together, they're enough.
The Attribution Models, Honestly Compared
- Last-click. Assigns 100% credit to the final touch. Easy to compute, easy to game, structurally biased toward bottom-funnel and branded channels. Still the default in too many GA4 dashboards.
- First-click. Mirror image of last-click — credits the discovery touch. Useful as a sanity check, rarely useful as a primary model.
- Linear. Splits credit evenly across touchpoints. Avoids the obvious biases of first- and last-click. Treats every touch as equally important, which is rarely true.
- Time-decay. Weighs recent touches more heavily. Reasonable default for shorter sales cycles. Less useful for considered B2B purchases.
- Position-based (U-shaped). Heavy weight on first and last touch, lighter weight on the middle. A useful compromise when you want to recognize discovery and closing without dismissing the middle of the funnel entirely.
- Data-driven attribution (DDA). GA4's default. Uses machine learning over your account's conversion paths to assign credit. Better than the rule-based models when you have enough conversion volume, opaque when you don't.
Server-Side Tracking and the CAPI Era
The deprecation of third-party cookies and the iOS App Tracking Transparency framework collectively gutted the client-side tracking model that built modern digital advertising. The replacement is server-side: events fire from your servers, with first-party data and identifiers, and get forwarded to platform APIs like Meta's Conversions API (CAPI), Google's enhanced conversions, TikTok's Events API.
Implementing this properly is one of the highest-ROI engineering projects most marketing teams have available. The components that matter:
