London-based mobile app seller GetJar created a stir today by releasing a study saying the mobile apps business will grow to $17.5 billion by 2012.

With 4 billion-plus mobile phone users around the world, that suggests an average of $4 per user generated by mobile apps.

Downloads of mobile apps will grow from 7 billion in 2009 to nearly 50 billion in 2012. The value of apps sold would then be greater than sales of music CDs, the study said.

Also predicted is a continuing shift away from "on deck" apps distributed by phone companies toward downloads from app stores, such as GetJar. The study predicted that on-deck applications' share of sales will fall to 23 percent, from 60 percent in 2009.

By 2012, Europe will be a bigger market for apps than the U.S., spending $8.5 billion versus $6.7 billion.

Asia now accounts for the most downloads, but consumers there spend far less on them than North Americans -- they're spending an average of 10 cents per app, vs. the $1.09 spent in this region.

The study predicts the overall average selling price of apps will fall 29 percent, from its current level around $1.90, but ad revenue from apps is expected to stay flat.

GetJar also predicted a shakeout in the number of app stores, which grew from eight to 38 last year and will continue growing this year.

"This report signifies a battle for survival of the fittest among app stores worldwide -- with app revenue and growth opportunities growing significantly," Chief Executive Ilja Laurs said in the release. "There is no way that this many app stores will survive in the long term and while the value of the global app economy is set to be astoundingly high by 2012, we think only a few app stores will share this revenue."

The study was done for GetJar by Issaquah mobile consultant Chetan Sharma. GetJar has other local ties; its vice president of sales, Bill Scott, is a Seattle native who used to work at InfoSpace.