I think your question, Kerei, needs to be clarified.
My guess is that you want to know (1) how many existing certified scuba divers are deemed CURRENT, and then (2) how many newly certified divers have JOINED in 2013. You may also want to know what past certifications no longer are valid. Hence, you can VOID them at your dive shop.
Somebody may beg the question ... what certifications do you accept? YMCA scuba diver from 1960? Well, this can be confusing to anybody who is running a dive shop. Specially if thousands of divers pass through your ocean pearly gates every year! Wow, what a challenge! Clarity of what is valid and not valid is important. That makes for great clarification, I am guessing.
Upon that pie of all divers ( new, current and void, ) there is a sub-count of how many current are PADI, NAUI,how many are newly joined in 2013 and what trends seem to be occurring. Are there more PADI divers? Maybe. If so, why?