Stitching and Attribution in GA4 vs Universal Analytics

© Source Medium 2023

Attribution is a method used in digital marketing to identity how much each marketing channel has contributed to your sales efforts. Where did your customer come from and what caused them to make a purchase?

By default (and by recommendation) GA4 uses “cross-channel data-driven attribution” which compares source, medium, and campaign combinations with user activity to deliver weighted results; combinations which were more important for driving a conversion are given more attribution. This is quite different from the methods of Universal Analytics, most commonly last-click attribution, which assign all the credit to the last touchpoint a customer had before making a purchase.

Changing attribution methods within Google Analytics will lead to sometimes dramatic changes in the apparent performance of your marketing channels and traffic sources! This will change what you see within Source Medium as well, as we reflect and report whichever attribution method you select during your GA4 setup.

When integrating data, it’s important to decide on a most trustworthy data source to use as a foundation. At Source Medium we use your ecommerce platform (such as Shopify) as our Source of Truth, as commerce platform data is robust and represents real financial transactions. When we integrate Google Analytics transaction data with ecommerce transaction data, we trust ecommerce data more than Google Analytics - this hierarchy of trust is called our “Attribution Waterfall.”

Source Medium stitches GA4 data with commerce platform data to improve on UTM coverage, which we then enrich with additional datapoints such as Zero Party data (Post Purchase Surveys) and other first-party identifiers to further represent your user behavior. This enrichment can fill in gaps in both data sources — Source Medium can regularly provide attribution for 10-30% more orders than Google Analytics on its own.

In the traffic module, Source Medium reports unaltered numbers directly from Google and doesn’t do any stitching between Universal Analytics and GA4 - this means before your business set up GA4, there will be no historic data! Outside of the traffic module, when Source Medium reports attribution data, we combine GA4 and Universal Analytics based on whichever has more complete data: For example, if GA4 has no information and Universal Analytics has information that says a user came from Instagram, Source Medium will attribute the user to Instagram. If GA4 and UA disagree and they appear to have the same amount of attribution, Source Medium will prioritize GA4.

Source Medium combines and deduplicates UA and GA4 traffic data by date, prioritizing data from GA4. In other words if session data exists in both UA and GA4, the UA data is simply dropped and the GA4 data is used. If UA data exists when no GA4 data exists, then the UA data is used.