App Store algorithm change said to be categorical

New third-party data suggests that changes made to Apple's App Store ranking algorithm last week were based not on how often users run applications, but how they are categorized within the directory itself.

That claim comes from Fiksu, a company that provides a "mobile app user acquisition platform," giving developers a way to gain visibility on Apple's App Store and the Android Marketplace. According to the company's data, which includes individual app rankings from the past year, Apple made a change just after midnight on April 14 to weigh some application categories more heavily than others.

"Downloads in certain categories are now weighted more heavily than others with respect to determining overall rank," the company said in an e-mail to CNET. "For example, apps in social networking were big movers in the overall rank charts, while apps in the games category did not appear to show the same gains."

The App Store has 20 categories, though the one for games outperforms all of them in terms of pure volume. Recent data from analytics firm Distimo covering a breakdown of the top 100 most popular applications during the month of February found games to be the leader on iOS and the Mac App Store, followed distantly by entertainment, utilities, and lifestyle applications. Each of these categories has its own ranking of top free and paid apps, separate from the overall top rankings, which Fisku says remains unchanged.

"This change should not affect intra category rankings and should have very limited impact on the overall rank," the company said. "However, apps in certain categories may experience a somewhat easier climb to the top of the overall rank."

Facebook in particular saw one of the most dramatic jumps following the changes, with blog Inside Mobile Apps tracking it jumping from the top 10s and 20s to No. 1. This was without any specific news hook or update that would prompt a surge, which raised some eyebrows. As of this posting, it's begun to drop back down and sits at the No. 8 spot. Though its move, along with jumps for applications like Netflix and Pandora are what prompted a look into whether Apple had made changes.

Fiksu founder and CEO Micah Adler told CNET that the move to re-weight categories could give applications in smaller categories a better chance at competing with the deluge of games, which frequently make up the majority of the top applications, but since Apple keeps its algorithm private, it's speculation at this point. Adler stressed that the company's findings clearly indicate that any ranking changes have not been based on how much applications are being used, which rival Google began practicing earlier this month according to the company's data.

"The clear proof is our evidence. We don't have access to the algorithm, so everything is evidence in one direction or another," Adler said. "(In Apple's case) we're not seeing any evidence of engagement directly being a driver, and we haven't seen much of a change within these individual categories."

Adler says Fiksu is in a unique position to gauge changes to Apple's App Store as well as Google's Android Marketplace due to its tracking technology and partnerships with ad and download networks like Google's AdMob. The company's core business is delivering scores of users to new applications, which Adler described as loyal. "We deliver users that stick around for quite some time," he said.

So far the company has a few dozen clients including Groupon, Hearst Magazines, TuneWiki, and Ask.com, and reports it has pushed 44 million user downloads of mobile applications. Reports emerged earlier today that Apple was combining the top apps re-weighting with the rejecting applications that made use of such services to get a user boost, though Adler said the company had not noticed that being the case with the company's clients so far.

Apple representatives did not respond to requests for comment on this story.