Yes, but it isn't easy. I am going to take level 13 for an example since it's the easiest. But basically in the world rankings if you go to it can tell you the story. If you look at the first page on the world rankings you will see the top 50 wrestler's. By doing a scan of seeing who is say ranked 2nd in level 12, that is the breaking point of where 12 ends and 13 begins. So at rank 37 is where last level 13 is since rank 38 is the top level 12.
Doing this is the only way to tell how many wrestler's are at each level. Easy? Heck no by any means, but it is possible.