Bruce Bawer:

...[A] study by a Swedish research organization, Timbro, which compared the gross domestic products of the 15 European Union members (before the 2004 expansion) with those of the 50 American states and the District of Columbia.

[...]

After adjusting the figures for the different purchasing powers of the dollar and euro, the only European country whose economic output per person was greater than the United States average was the tiny tax haven of Luxembourg, which ranked third, just behind Delaware and slightly ahead of Connecticut.

[...]

If the E.U. was treated as a single American state, it would rank fifth from the bottom, topping only Arkansas, Montana, West Virginia and Mississippi. In short, while Scandinavians are constantly told how much better they have it than Americans, Timbro's statistics suggest otherwise. [Via Political Diary.]