comScore reported that 15.4 million iPhones were in use in the US as of November. (25% share of 61.5 million total smartphones.)
We also know that about 75 million iPhones were sold by November since the product launched. With about 17 million units older than two years, and assuming that half of those might still be in use and that all the iPhones less than 2 years old are still in use, we get an upper bound of 66.5 million iPhones in use globally.
That means 23% of all iPhones are in use in the US and that 77% are in use outside the US.
Can this be verified?
The sell-through data we have supports a slightly lower figure.
October 2010: 63 percent of iPhones were sold outside the US in Q3
April 2010: Non-US iPhone sales approaching 70% of volumes
This might indicate that comScore surveys under-represent the iPhone or that device attrition/retirement is significant. However, the data does seem to imply that the US is no more than one third and perhaps as little as one quarter of the iPhone’s user base. Perhaps with Verizon, that figure will grow. But at the same time, new international markets (like China) may continue to outgrow the US.
The 4:1 split could continue. After all, the US represents only 234 million out of about 5 billion mobile phone users globally–a mere 4.7%.