Apple announced today that 2 billion iPhone and iPod touch apps have been downloaded since the App Store launched on July 11, 2008.

As the number of apps (now 85,000) and number of iPhones and iPod touches sold (now 50 million) have increased, the rate of apps downloaded per day has increased, too.

Since Apple announced that 1.8 billion apps had been downloaded on Sept. 9, iPhone and iPod touch owners have downloaded an average 10.5 million apps per day. That's much higher than earlier this year, when about 5 million apps were downloaded per day, or this time last year, when about 2.3 million apps were downloaded per day.

Meanwhile, any guesses as to the cause of the uptick in September? Timing of the announcements certainly plays a role, as does Apple's rounding to the nearest 100 million. But it's a rather steep increase in the daily download rate.

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