How Android finished the iOS mojo in 5 years

The Mobile OS marketshare compared by year from 2009 to 2013. Observe the growth of Android. From a 4% marketshare to  78% market share in 4 years.Android has been growing exponentially from 4% to 27% to 46% to 66% and in 2013 at 78%  from 2009 onwards. iOS is number 2 and has seen its market share  almost flat ..during the last 5 years