In the buildup to tomorrow's Google I/O conference, App Annie has released a report detailing the rapid growth of Google's Play Store and the revenues it's producing. After surpassing a million apps last summer, Android's app repository now has more than 1.5 million, with downloads reportedly growing by 50 percent between 2013 and 2014. Income from those apps is increasing at an even faster pace, more than doubling last year's totals. What's notable about that growth is that it's being driven almost entirely by freemium apps — free to download, but including paid in-app purchases — which now produce 98 percent of all revenues from Android apps and games.

Japan maintains its lead as the world's biggest spender on in-app content, driven primarily by addictive mobile games, with the US and South Korea following in a distant second and third spot. Games aren't influential just in Japan, however: they account for roughly 40 percent of all Android downloads and generate almost 90 percent of the platform's revenues. Asian markets are leading the way in embracing the freemium model in games and the rest of the world is following a similar trajectory. Android's users might still be reluctant to pay for apps, but content inside those apps is apparently proving much more enticing.

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