Horace Dediu takes a look at the growth rate of Android in the United States in comparison to the rest of the world in a great blog post.

The more startling thing is the difference in growth: it implies that with a US growth rate of only about 13.3k/day, global growth is 150 times faster than US growth. In other words, that 0.6% of new users are in the US and that 99.4% of Android growth is outside the US.

This fact says very interesting things about where Apple needs to prioritize development of additional iPhone models.