54% of Wikipedia pages contain at least one link in their “References” section that points to a page that no longer exists.
It would be interesting to know how many of these references don't exist anymore and how many have just moved. Web has come a very long way since 2013 and I bet that websites hosting the references have undergone several iterations altering the URLs in some way.
but they'll keep collecting that data even after the slap on the wrist which will be more like a gentle tap