When analyzing data in GA4-BigQuery, you may wonder why the values of collected_traffic_source and session_traffic_source_last_click do not match. These two fields provide valuable information about user paths, but they serve different purposes and can lead to discrepancies.
1. Different Purposes of the Fields
collected_traffic_source indicates the source of traffic for a specific event, while session_traffic_source_last_click replicates the last-click attribution logic from GA4 and captures the last source used by the user before conversion within the session.
2. Reasons for Discrepancies
Since session_traffic_source_last_click is based on last-click attribution logic, it’s essential to understand where discrepancies may arise. Here are a few possible reasons:
Specific Attribution Window Settings: If the attribution window is set incorrectly, some interactions may not be tracked properly. For example, if the window is too long, users may be attributed to sources from a long time ago.
Custom Session Timeout Settings: If you have a short session timeout configured, this might result in new sessions being created too frequently. This can also cause discrepancies between the values of collected_traffic_source and session_traffic_source_last_click.
While session_traffic_source_last_click is a convenient shortcut for attribution calculations, it’s often better to use collected_traffic_source when dealing with complex custom models to gain more accurate insights into user behavior.
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