[Plugin: Google Analytics for WordPress] Outbound links under-reporting

I’ve been using Yoast’s Google Analytics for WordPress plugin for a couple of years.

I use its feature to measure outbounds as Events. It’s useful. My sites have many thousands of outbounds each month.

However, I’ve recently been able to compare outbounds from my site to 5 or 6 other sites with data from those 5 or 6 other sites.

These show that Referrals from my site are in fact much higher – by a figure averaging at 70% higher – than my GA figures.

So the Yoast plugin is under-reporting significantly.

Any thoughts about why this is happening, and possible workarounds?

Or suggestions or more robust reporting mechanisms for outbound links?

thanks

Mark