The reason for this would be that GA filters out bot traffic differently than other vendors. That includes legitimate bots like search engine crawlers. Web anal

The reason for this would be that GA filters out bot traffic differently than other vendors. That includes legitimate bots like search engine crawlers. Web analytics are just not that accurate. The number quoted by the Xoogler in an analytics manual I recently went though is an expectation of ~10%+ wiggle. GA is always going to show 'lower' numbers than straight logs in particular because of this.