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:

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.

I should note that author stats was removed before but it did come back eventually.

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.

Forum discussion at Google+ and Google Webmaster Help.