I will start a major project and I have to choose which version of iOS SDK I need to target. For that, I would have recent statistics on the use of ios 5 and 6 on the iPhone.
Where can I find these statistics?
Most people seem to follow the stats reported by David Smith here:
http://david-smith.org/iosversionstats/
However, it all depends on your audience and how long it will take you to develop your app.
Apple also has a page showing AppStore version statistics which is kept up-to-date:
I think there is a strong case at the moment to target iOS 6 and later versions only. Many people have updated thanks to Apple's over the air updates, and iOS 6 has been out for quite some time already.
Also bear in mind that certain older devices like the iPad 1 are not able to install iOS 6.
来源：https://stackoverflow.com/questions/15967143/where-can-i-find-ios-versions-statistics