Social and mobile gaming companies are ever more dependent on so-called ‘whales,’ who make up a tiny fraction of the overall player base but can account for two-thirds of gaming revenue.

San Francisco-based mobile marketing automation firm Swrve recently released its 2015 Mobile Monetization Report, which crunched the data of 20m free-play mobile gamers across 40 different game titles during the month of January.

The data shows that just 2.3% of all players made an in-app purchase with real-money, or what gaming firms refer to as ‘bookings.’ Even more staggering, a mere 0.23% of players accounted for 64% of bookings revenue.

Social gaming’s reliance on ‘whales’ has long been recognized, but Swrve’s data is even more startling than the 2012 Macquarie Securities report which showed 0.5% of Zynga players accounted for 70% or more of the company’s non-advertising revenue.