He claims " 54% of the 45M devices are in the US which means ~ 25M devices. The US has about 300M people. That means about 8% of the general American population has one of these devices."

However, this doesn't take in account broken phones or people upgrading iphones (and then not cycling the old phone back into the market place).

I would guess this number is 30% higher than it should be, at least.