What percent of the world is pagan?

That depends on your definition, if you mean to use the Christian definition of "anyone not beleaving in the god of Abraham" then that would be everyone but Christians, Jews, and Muslims. Roughly 45 to 50 %.

If you mean Neo-Pagan, as in Wiccan or a reconstruction of a European pre-Christian religion then your talking well bellow .1%. Neo-pagans are less than .33% of the U.S. population of 300+ million and even with European Neo-pagans that's a rather small amount.