You should include iPod Touch and how apple forces a charge for updates on that device.
This chart is also skewed a bit and should be based on intervals of releases rather than "years since". I don't recall seeing any iOS5 backports to iPhone 2G or 3G.
This chart is also skewed a bit and should be based on intervals of releases rather than "years since". I don't recall seeing any iOS5 backports to iPhone 2G or 3G.