This is yet another thread on evaluating language proficiency, but in particular, I've been wondering about this: Suppose you're studying an endangered language or some language for which proficency tests are simply unavailable. If you speak some of that language, then how do you evaluate your proficiency in it? Is it possible that the proficiency scale (whether you use the A1-C1/C2 scale or the four-star system) doesn't really work for all (or even most) languages?
Also, is it possible that native speakers of one language may have a greater or smaller vocabulary on average in their language than native speakers of another do in theirs? For example, I've kind of mentioned how in the US, if you want to go to college, you have to take an entrance exam called the SAT, and passing it requires a fairly large English vocabulary. However, I somehow doubt that very many native speakers of Malayalam, for example, have a similarly large Malayalam vocabulary.