In December 2011, Google launched author stats, a way to see how your content, across sites, based on your Google Authorship profile, fared. That is now gone, there is no way to access those reports anymore.
Glenn Gabe was the first to spot this and posted it on Google+ saying:
Google Author Stats Is Missing! Removed From Google Webmaster Tools. And that's after sitting since 7/9 without being updated. I was going to write a post about that, but now it's completely gone. Yes, author stats leads to a 404 page in GWT. Is it simply a glitch or is there something else going on?
Yes, trying to access it directly does 404, here are screen shots from Glenn:
The link is now missing from Google Webmaster Tools:
If you try to access it directly, the page will 404:
I emailed Google about this yesterday and pinged some folks on the Webmaster Tools team and have not heard back.
This seems a bit more permanent, since we know Google dropped author images back in June of this year and Google claimed it had no impact on CTR, but the stats showed otherwise.