By transplants what do you mean? With the exception of a small percentage pretty much everyone on the island is a transplant of some kind. If you mean gringos I doubt that anyone has that kind of information, not even the government.
As far as regular posters to this board you're probably looking at a dozen or so.
Average age here overall is probably somewhere in the late 20's. Gringo's are probably in the early 40's on average. This is all a total guess as there's no resource.