Why No Attribution Model Is "Correct"

Every attribution model is a set of rules for assigning credit across touchpoints that all contributed to a conversion in reality. None of them measure the truth perfectly — they approximate it, each with different blind spots. The goal isn't finding the "correct" model; it's picking one that's honest about its tradeoffs and consistent enough to compare campaigns over time.

Last-Touch: Simple but Blind to the Top of Funnel

Last-touch attribution gives full credit to the final touchpoint before conversion. It's simple to implement and easy to explain, which is why most teams start here. Its weakness is systematic: it undervalues every channel that plays an introduction role — usually social and display — and overvalues the channel that happens to close the loop, usually search or direct.

First-Touch: The Mirror Image Problem

First-touch attribution flips the bias, crediting whatever brought someone into your world first. It's useful for understanding what's driving new audience discovery, but it ignores everything that actually pushed someone across the line to convert. Neither first- nor last-touch alone gives you the full picture — they're deliberately partial views.

Linear and Position-Based Models

Linear attribution spreads credit evenly across every touchpoint in the path. Position-based models (often 40/20/40) weight the first and last touch more heavily than the middle. These middle-ground models reduce the extremes of first- and last-touch bias, at the cost of being harder to explain to a stakeholder who wants a single clean number.

Multi-Touch Attribution and Its Real Cost

Multi-touch attribution uses statistical modeling to assign fractional, data-driven credit across the whole path. It's the most accurate approach in principle, but it requires meaningful cross-channel conversion volume and solid tracking infrastructure to work well. Building it before you have that volume just produces a more sophisticated-looking wrong answer.

Choosing a Model You Can Actually Defend

The practical answer for most teams: start with last-touch because it's simple and consistent, but review it periodically against first-touch or linear to catch channels that are being systematically undervalued. Upgrade to multi-touch only when the business has outgrown what simpler models can honestly tell you.

Conclusion

Attribution isn't about finding a perfect answer — it's about knowing exactly what your chosen model is blind to, so you don't make budget decisions based on a blind spot you didn't know you had.