In early July, downloads on the App Store topped 15 billion, but Google's Android is now giving Apple's store a run for its money. According to recent stats from ABI Research, Android took the lead in worldwide mobile app downloads during the second quarter.
Of all the apps downloaded, Android now accounts for 44 percent while iOS has 31 percent of the market, ABI said.
"Android's open source strategy is the main factor for its success," Lim Shiyang, an ABI research associate, said in a statement. "Being a free platform has expanded the Android device install base, which in turn has driven growth in the number of third party multi-platform and mobile operator app stores."
Another explanation could be the slowdown in iPhone sales last quarter as people waited for Apple to release its next-gen smartphone. Apple iPhone shipment growth dropped from 15 percent to 9 percent over the quarter, while Android shipments jumped 36 percent. But with the release of the iPhone 4S—4 million of which have already been purchased—those numbers are likely to pick up.
And as ABI pointed out, Apple users are still downloading more apps per person than their Android counterparts.
"Despite leading in total mobile application downloads, Android's app downloads per user still lag behind Apple's by 2-to-1," said Dan Shey, practice director for ABI's mobile services. "Apple's superior monetization policies attracted good developers within its ranks, thus creating a better catalog of apps and customer experience."
Overall, mobile users are expected to download a staggering 29 billion apps in 2011, up from 9 billion in 2010, thanks to the proliferation of smartphones.
The growing popularity of Android, however, has resulted in an influx of malware. An August report from Lookout Security found that app- and Web-based threats are increasing in prevalence and sophistication, with Android users 2.5 times more likely to encounter malware than they were six months ago.
Unlike Apple, Google does not monitor its apps once they are in the Android Market, responding only to complaints.
"We don't generally go back and try to make sure that every app does what it says it's going to do. [Google is] really trying to maximize the ability of small app developers to get online," Alan Davidson, director of public policy at Google, said during an appearance on Capitol Hill earlier this year.
For more, see PCMag's 50 Best Android Apps slideshow above.