I am not sure about the clickie population, but I believe I heard something about lego minifigs greatly outnumbering the human population on this green earth, by three or four times even.
Seeing how clickies are available in less countries but existed earlier than lego minifigures and have many sets dedicated to a single clicky, I am guessing there might be as much clickies as people in the world.
Might be a great question to ask Playmobil though, I am sure the company would know how many clickies have been produced, not counting the fatality rate amongst clickies.