Apple announced yesterday that downloads in the App Store had topped 40 billion. (Apple gave no specific date for when the milestone had been reached.)
In any case, that's up from 35 billion in October and 30 billion last June. Overall, App Store downloads doubled in the past year alone.
Using an exponential trend line, we predicted in October that downloads would hit 40 billion by the end of 2012. If they maintain their current growth trajectory, downloads will top 55 billion by by mid-2013.
Source : Business Insider SAI January 2013