I agree with the points made but I don't believe the incomes of Swedish in Sweden vs. the US are a great evidence to support them. I would expect the incomes to be higher in the US for the following reasons:
1. It probably takes an above-average income to start with to actually relocate from Sweden to the US.
2. Would they leave their homeland if the financial prospects weren't better ? Some might, but I'd guess most would not.
3. There would be few low-income people coming seeking welfare-type benefits (since the benefits they would be leaving are likely greater) and more high-income earners looking to excape taxes.
4. Tiger's ex and the divorce settlement provbably skew the data. (She is Swedish, isn't she?)