With titles like Angry Birds Space being downloaded by the tens of millions, it's no secret that mobile gaming is on the rise, so researcher Newzoo set out to gather specific figures in a study that included the top 200 grossing mobile games and survey results from 17,000 respondents. The outfit found that the US mobile gaming market has grown from 75 million to 101 million mobile gamers, with 69% of them playing on smartphones and 21% on tablets (there's no mention of conventional handheld consoles).

Not only are there more players, but an increasing percentage of them are willing to pony up. The number of paying players has reportedly grown 35% to 37 million Americans, or 36% of all mobile gamers. Of American gamers, 19 million play on an iPhone, 18 million play on an iPod touch and 12.7 million play on an iPad (many people use multiple iOS devices). As of last month, Apple's mobile devices earned 84% of revenue generated by the top 200 grossing games, leaving Android with a 16% slice in the US.

Interestingly, a majority of that cash (91% for both iOS and Android) stems from microtransactions inside the game, not purchasing titles outright. Besides user demographics, Newzoo CEO Peter Warman says there's one difference between iOS and Android that could explain the revenue discrepancy: Apple requires users to link credit card information to their accounts. "I can hardly imagine any other company in the world that would be able to get away with this, including Google and Microsoft," Warman said.