If you're thinking about launching an app to make your millions, then perhaps you need to think again, especially if you plan on producing an app for Apple's App Store.

Figures from the US show a thirty percent fall in March downloads to the top 200 free iPhone Apps as the "novelty factor" of the iPhone 4S begins to fade. Statistics from mobile app marketing business Fiksu's App Store Competitive Index (which measures the average aggregate daily download volume of the top 200 free US iPhone apps) show downloads dropped by almost two million from 6.35 million per day in February, to 4.45 million in March.

The reasons for the sudden drop in downloads are unclear, but Fiksu believe it's partly down to users finally getting bored of their new Christmas toy, and a move by Apple to clamp down on app store manipulation.

iOS App downloads Fiksu Aug 2011 to March 2012
iOS App downloads Fiksu Aug 2011 to March 2012

Micah Adler, Fiksu CEO explains, "With the novelty factor of the iPhone 4S launch and the holidays well behind us, and no other events in March to spark discovery, March's download dip was expected," Adding, "An unexpected contributing factor could be the decline in the use of robotic install tactics by app marketers responding to Apple's new policy. The decline in competition and steady costs definitely presented app marketers with a ranking opportunity in March, driven largely through the cost-effective conversion of organic users into loyal users."

Businesses keen to get to the top of the App Store charts have taken to employing firms who use automated robotic installs using "bot farms." The systems are designed to make automated, recurring downloads of free iOS applications to push applications into the top 100 of the App Store's bestseller lists, in the process pushing the app in front of a larger audience.