I was wondering if there is some research on the number of mistakes made by native speakers in certain languages? I think that since some languages are more complex (their grammar is more complex) and some are less it can be that native speakers of complex languages make more mistakes in their speaking and writing.
My native language is Russian, and I also speak English and French fluently. I see that average Russian people often make mistakes (wrong declension, wrong stress, wrong punctuation). And as I can see English and French people make less mistakes.
I think linguists should introduce some kind of an index of mistakes made by native speakers to measure complexity of a language.