http://www.lifehack.org/305085/7-timeless-tips-learn-any-language-days-not-years
the 75 most common words make up 40% of occurrences
the 200 most common words make up 50% of occurrences
the 524 most common words make up 60% of occurrences
the 1257 most common words make up 70% of occurrences
the 2925 most common words make up 80% of occurrences
the 7444 most common words make up 90% of occurrences
the 13374 most common words make up 95% of occurrences
the 25508 most common words make up 99% of occurrences
