They use purchasing power parity indexes, which are notoriously opaque. Here are the global top 20, using Eurostat's per capita numbers, based on 2003 data and current exchange rates (1.2 $ = 1 EUR):
Region Annual EUR per capita ------------------------------------ Luxembourg 48,919 Norway 39,366 Switzerland 36,571 Denmark 33,670 US 31,391 Japan 30,562 Ireland 29,158 Sweden 27,912 Netherlands 26,573 Finland 26,231 Austria 25,879 Germany 25.037 Belgium 24,714 France 24,341 UK 23,481 Canada 21,196 Italy 21.011 Australia 20,088 Hong Kong 18,831 Israel 18,800
Note that the US advantage disappears completely when you factor in total working hours -- the EU countries have shorter annual working hours, 10-15% less than the US on average.
-- DRR