What is Attribution Drift?

Attribution Drift is the percentage gap between what Google Ads claims as conversions and what GA4 confirms, measured per campaign over time.

Why it matters

A stable, explainable gap between platforms is normal — they measure differently. Drift is the dangerous version: the gap growing or swinging campaign by campaign, which means bidding decisions are increasingly based on conversions your analytics cannot reproduce.

How ClickCatalyst detects it

Drift is computed per campaign as the percentage difference between Ads-reported and GA4-verified conversions, tracked across 7-day and 30-day windows. Campaigns with high phantom share AND high spend are flagged first — that combination does the most damage to bidding accuracy.

Drift feeds two downstream verdicts: the Bidding Trust assessment in the Tracking Mismatch audit and the Signal Health Score in the AI Max Signal audit.

drift_pct = (ads_conversions − ga4_conversions)
            ÷ ads_conversions × 100   // per campaign, 7d & 30d

Example

A campaign with 27% drift and the account's largest budget is a worse problem than a campaign with 60% drift and $50/month spend — drift is always weighted by the budget it steers.