How to Express This?

English, unlike some other languages, doesn't really have the ability to make up words and terms for stuff like that :-)

I would say "One hundred of the most economically powerful countries in the world" or so :-) You could make up your own and say "The world's oligarchy" or so, but there's no single word or set phrase that I know of. . .

Anyone else?

I agree with you, Princessash; there's no one set word of expressing that. For clarity, I'd use the first answer that you gave; to be lyrical, the second, or something like the world's élite.

I meant "county", not "country".
Princess, if I say "this county is one of the one hundred of the most economically powerful counties in the nation", does it work? I feel using "one of the one..." seems retarded...

Finally, thank you both.

You could say, "This county is in the top one hundred most economically powerful counties in the nation."

I would say "this county is one of the hundred most powerful in the nation"

so, yes, leave out the "one"

You might say "one of the 100 most affluent counties in the nation" if you wanted to be a little more succinct.

And yeah, the 100 would be written out as "hundred" and not "one hundred".

Thank you all!