...we tend to act as if there is one anyway. That is, we place a lot of focus on GDP per capita when evaluating economic success. By this measure, the US is, of course, successful. By a slightly different measure from the OECD (go to page 37), average disposable income per household, the US ranks second after Luxembourg among the nations measured. Luxembourg has about the same population of Long Beach, so it is hard to worry too much about it.
But a social welfare function that looks at the lowest decile of income is just as legitimate (or perhaps I should say, illegitimate). By this measure, the US ranks 20th among countries measured, which places it toward the bottom of the OECD pack, with levels similar to Greece and Italy.
On the other hand, the top 40 percent of American household are better off than their counterparts in all other countries (with the exception of Luxembourg), reflecting a great deal of affluence across a large number of people. So where to pick? As Arrow would say, that is really impossible.