not to mention that eu+us+uk does not equal the so-called '1st world' in it's entirety (see also: canada, japan), and also that there is some notion of a '2nd world' as well.
The confusion stems from the fact that most people perceive it as a "measure of economic development", while in fact it's political cold war terminology:
First world = US + close allies
Second world = USSR + close allies
Third world = Everybody else
