Affiliate attribution may drop in Google Analytics 4
The introduction of Google Analytics 4 (GA4) has brought about significant changes in the way attribution is handled, impacting the affiliate marketing channel alongside other sources.
Google officially deprecated Universal Analytics (UA), the predecessor to Google Analytics 4 on July 1, 2023. The new GA4 brings with it new tracking methodologies and reporting focusing on events and parameters (unlike UA's sessions and pageviews). Most importantly it also brings about new Attribution Models - this is where the problems start.
There are numerous reports now circulating that GA4 under-reports attribution to non-Google marketing channels when compared to Universal Analytics.
Most crucially utm_source parameters, widely utilised for attribution and cross channel deduplication throughout affiliate campaigns, are de-prioritised against Google's own Ads under-reporting the channel. See UTM overriding paragraph on this article
Recommendations for Affiliate Campaigns with GA4
Based on the above information provided by Google and on research conducted by various parties (readily available with a quick search on Google) our recommendation is that the DDA in GA4 is not suitable for Affiliate Tracking. Advertiser's should instead utilise "Last Click" attribution to ensure an accurate measure of all sales channels.
For Optimise Advertisers if you require support in configuring your GA4 account or testing its effects to your campaign please reach out to your Account Manager.