[whatusername]

Not over 1 billion people it's not.

There's a lot of families that use hand-me-down phones.

Consider the scenario where Mum gets a new Phone every 2 years and Dad gets her old one when she's done. The phone has a 4 year life.

Averaging it out (over the richest 1billion people in the world) and 3 years is possibly a pretty close figure.

[cryptoz]

I highly doubt the richest 1 billion have anything at all to do with the majority of Android phone purchases. Countries like Nigeria (140,000,000 people) and Kenya (40,000,000 people) are starting to see their populations going from no-computers to everybody-has-a-smartphone. Most people there may never own a PC but will move straight to cheap, open source smartphones.

I would bet that Android's growth numbers are a majority of new users and a minority of returning users. The platform's only been popular for a single "update cycle" anyhow. 3G networks are popping up in the poorest parts of the world and people are buying phones there.