Trouble with Google Analytics tracking of third-party ad links

Google Analytics is widely accepted as an accurate and impartial source of web traffic.

However, I have found that it fails to track many of the clicks from banner ads in email newsletters. I’m seeing instances of situation where only 5% of clicks are recorded in GA.

At first I suspected shortened links were causing the issue. However, even when complete links with UTM parameters are used, only a small fraction of the traffic is recorded.

This continues to be an unresolved issue.