The group of gamers responsible for half of all in-game revenue in mobile titles is frightening because it is so narrow, according to a survey by Swrve, an established analytics and app marketing firm. About 0.15 percent of mobile gamers contribute 50 percent of all of the in-app purchases generated in free-to-play games..

http://venturebeat.com/2014/02/26/only-0-15-of-mobile-gamers-account-for-50-percent-of-all-in-game-revenue-exclusive/