When is platform-reported ROAS roughly accurate?

For cold prospecting to audiences with no prior brand relationship, for channels running alone in a region where no overlap exists, and for short-consideration direct-response purchases. In all three the proximity story and the causal story are genuinely close.

What does it mean if a channel's reported and causal ROAS agree?

Usually that the channel is doing acquisition rather than harvesting existing demand. Convergence is evidence the channel is creating the purchase; divergence is evidence it is appearing near purchases that were going to happen anyway.

Should brands with long consideration cycles expect bigger gaps?

Yes, as a matter of course. A long gap between first touch and purchase leaves room for many influences, so credit allocated by proximity diverges further from a counterfactual estimate. That is structural rather than a sign of a problem.

Where reported and causal ROAS agree more than you expect

Everyone expects the gap. Fewer people notice where it almost disappears, and the places it does are the most informative part of the comparison.

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By Joris van Huët, Founder & CEOUpdated 2026-10-063 min read

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The gap between reported and causal ROAS is not uniform, and the channels where it nearly vanishes tell you more than the ones where it is large. Nobody expects agreement, so it goes unexamined.

Three places they converge

Situation	Why the numbers come close
Prospecting to genuinely cold audiences	Proximity and causation point the same way
A channel that is the only one running in a region	No overlap to inflate the claim
Direct-response channels with short consideration	Little room between the touch and the purchase

Cold prospecting

When a channel reaches people who had no prior relationship with the brand, the story that the touch caused the purchase and the story that the purchase would not have happened otherwise are close to the same story. Reported and causal estimates converge because the underlying situation genuinely is what the reported number assumes.

This is the useful diagnostic: convergence is evidence that a channel is doing acquisition rather than harvesting. Divergence is evidence of harvesting. That reading is more actionable than either number alone.

The single-channel region

If a channel runs in one market and nothing else does, there is no overlap for other platforms to claim, so the reported figure is not inflated by double counting. It may still be inflated by view-through generosity, but one of the two sources of distortion is absent.

This is also the natural experiment worth looking for in your own history. A regional launch, a market where you paused everything else, a period when a platform was down: each is an accident that behaved a little like a holdout test. The geo testing guide covers how to use them deliberately.

Short consideration cycles

For impulse-priced products bought within a session, there is little distance between the touch and the purchase for other influences to occupy. The gap narrows because the causal story is short.

The corollary is that brands with long consideration cycles should expect large gaps as a matter of course, and should not read them as evidence of anything unusual.

Why the pattern matters more than the levels

Any single channel's gap is noisy. The pattern across channels is stable, and it maps onto something real about your marketing: which channels create demand and which harvest it. That is a strategic question, and the comparison answers it almost as a by-product.

The check to run

Sort your channels by the size of the gap and ask whether the ordering matches your intuition about which ones create demand. Where it does, you have a coherent picture. Where it does not, you have found the interesting question of the quarter.

Two further reads on the mechanism: platform attribution overcounting for why the gap opens, and incremental versus attributed revenue for what the two quantities actually are.

Frequently asked questions

When is platform-reported ROAS roughly accurate?
For cold prospecting to audiences with no prior brand relationship, for channels running alone in a region where no overlap exists, and for short-consideration direct-response purchases. In all three the proximity story and the causal story are genuinely close.
What does it mean if a channel's reported and causal ROAS agree?
Usually that the channel is doing acquisition rather than harvesting existing demand. Convergence is evidence the channel is creating the purchase; divergence is evidence it is appearing near purchases that were going to happen anyway.
Should brands with long consideration cycles expect bigger gaps?
Yes, as a matter of course. A long gap between first touch and purchase leaves room for many influences, so credit allocated by proximity diverges further from a counterfactual estimate. That is structural rather than a sign of a problem.

Go deeper: Causal attribution, explained.

Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.

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