Why does user's cookie consent decision affect GA page view counts?

Question

After a modification in our site's cookie consent, percentage of users accepting the GA cookies increased about 40% (before the change: 50% opt-in, after the change: 90% opt-in).

EDIT The modification we made was to remove the "Deny All" button. Now there's only an "Accept" and a "Settings" button.

Since this change the page views reported by GA increased about 40-50%.

AFAIK the "missing" consent opt-ins are estimated by GA. Therefore I wouldn't expect any remarkable change of reported page views even if the number of users accepting GA cookies increase.

Question: which page view counts are more accurate? The one's before the consent change or the one's after the change?

Answer 1

There's different types of missing data in Google Analytics.

1. Data lost to ad blockers and similar - Google should not be getting this data, though I'm sure they try.
2. Data lost to lack of cookie consent - Google have recently added "advanced consent mode" to allow them to fill in the gaps of people who opt out-of cookies. Previously this data was lost, now it is estimated based on certain user events that ping Google.

Google say

To mitigate any data collection gaps, Google products use these pings to model your metrics for your measurement solutions.

I assume these will be the estimates you are talking about. I've seen people suggest more complex modelling going on to fill in the gaps, but never found reference from Google themselves or detail beyond "AI", so that's probably just hearsay.

Neither page counts will be completely accurate, as ad blockers are increasingly common. However, assuming your change was to add Advanced Consent Mode, the latter should be more accurate.