Your analytics only sees half your visitors
42% of visitors reject cookies (40–45% in the Nordics, more on mobile). Your conversion data describes the half that accepted – and they are not a random sample.
Cookie opt-out rates now average 42% worldwide, and 40–45% in the Nordics. Mobile visitors reject 10–15 percentage points more often than desktop, and a single-click "Reject all" button pushes rejection up another 25–35 points.
That means your GA4 conversion rates and A/B test results describe only the half of visitors who clicked accept – a group that skews desktop, older, and less privacy-aware than the people you are actually trying to convert.
Why it matters: a "winning" variant or a sudden mobile conversion drop may just be a measurement artefact. Cross-check consented analytics against server-side or cookieless counts before you act, and never compare periods on either side of a consent banner redesign as if nothing changed.
Source: Cookie Consent Statistics 2026: Opt-Out Rates, Banner Fatigue, and Data Loss
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