Originally Posted by
docbert
Around 25% of all Australian residents were born overseas.
Over 50% of all Australian residents were either both overseas and/or have at least one parent that was born overseas.
For the US, the first number is closer to 10%. Not sure about the second.
So whilst it doesn't account for the full 40%, it definitely accounts for some of it.
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According to the ABS, the 2006 census showed that 44% of Australians were either born overseas or have at least one parent born overseas (23% actually born overseas), according to Wikipedia 12.6% of Americans were born overseas (can't find the other figure for Americans, and don't always trust Wikipedia). So there's still a significant gap. (Next time an American starts to lecture about being the world's most diverse nation, built on immigration yada yada I'll have a come-back!)
As an aside, I myself don't come under either category and have owned a passport since I took my first overseas trip aged 14, same as my sister.