The second hand market for iPhones is quite large in Australia and I imagine its the same elsewhere. Probably not fair to only include those two years iPhone sa

The second hand market for iPhones is quite large in Australia and I imagine its the same elsewhere. Probably not fair to only include those two years iPhone sales. I would think at least 50% of the older models are either on-sold or the user hasn't upgraded. edit: UVB-76 has a good point, there is probably a very high percentage overlap.