the biggest problem with editor retention at the moment is the second edit.

True. The ratio of new users over the past month with one or two edits to those with three or more would make a great new metric. I hope it shows up on the report card.

Thanks to Jonathan Morgan for investigating adding new users with fewer than ten edits who've used the "<ref" tag to the Teahouse invitation list. I am sure that will be well worth the effort.