I was unhappy with Zanata's statistics as it's not having a global overview of translations in one language (please see https://l10n.gnome.org/teams/fr/ to have an idea of something helpful).
With the API, I decided to try to get some more information.
Despite the fact that API is pretty bad (I get many errors 415 I don't understand), I was able to get information project by project.
You can download the actual translation statistics at :
If you want to see/improve the code (especially the list of project/iteration), please access the link :
Programming is not my profession, I'll be pleased to be advice and help.
If something better exists, I'm also interested.