Tim Cook on the 55 million iPads sold to date:
This 55 is something no one would have guessed. Including us. To put it in context, it took us 22 years to sell 55 million Macs. It took us about 5 years to sell 22 million iPods, and it took us about 3 years to sell that many iPhones. And so, this thing is, as you said, it’s on a trajectory that’s off the charts.
That gave me an idea. Here is a plot of each major computing product Apple sold throughout its history shown as a cumulative total since product launch.
The iOS platform as a whole reached 316 million cumulative units at the end of last year. The iOS platform overtook the OS X platform in under four years and more iOS devices were sold in 2011 (156 million) than all the Macs ever sold (122 million).