Hello Gregor,
Although the number is quite high as with other type of instructors (certified/uncertified/undocumented), I couldnt put a figure to it. This question may best be answered via a Google Search.
Wrong forum for this question. But I /agree with the above posts. Without a certifying body controlling who does what there is no way to tell who is certified to hold this position.
I have the same response as I had to your question about the number of CrossFit instructors in the U.S. Contact the Zumba link Joanne included in her response and they may well be able to give you the number of instructors they have franchised to teach the Zumba program.
