I found a nice site calculating one’s vocabulary in English language by asking whether you know certain rare words. Try it:
I believe vocabulary correlates to one’s IQ, but have no idea how much that correlation is.
I am not a native, but I tried the test. My results is only 6800 words.
There is a statistical information in that site too.
And the blog with statistics:
It correlates with SAT scores, too.
So please answer the polls on how much your vocabulary was, created for native and non-native seperately.