Though I’m not sure whether this question is suitable to EL&U site or not, I’m glad if I can get any input on the relationship of the vocabulary and comprehension of English language, or if you can suggest me other suitable site that I can post this question.
I recently read the book, titled “Read a Million Words (to master English language),” written by Japanese English language scholar at Tokyo Tele-communication University, Kunihide Sakai.
Mr.Sakai cites the following numbers:
Vocabulary of 1,000 words allows 80% comprehension of English statement
2,000-word vocabulary allows 86.6 % comprehension of English statement
3,000-word vocabulary allows 90.6 % comprehension of English statement
4,000-word vocabularies allows 92.8 % comprehension of English statement
Though it’s not clear what "English statement" means (maybe I’d do better to ask him directly as well as about the source of number), it’s hardly believable that 3,000 vocabulary level allows 90% comprehension of general statement in English language from my experience of reading English language literatures everyday to look for the subject for posting EL&U.
I know British psychologist and linguist, Charles K. Ogden asserted that we can express everything we want to say with 1,500 words (850 basic English words and their combinations, plus 350 international (foreign) words and 300 from scientific terminology), and promoted Basic English movement during 1930s.
Winston Churchill supported Ogden’s theory and recommended diffusion of Basic English as the international language in his discourse at Harvard University in 1944. However, Ogden's theory is applied only to writing and speaking, not reading and hearing.
Is there any trustworthy study that illuminates the relationship between vocabulary level and ability to comprehend English language statements expressed in day-to-day conversation, literature (not too academic) and daily journals? What is its finding with regards to the relationship between vocabulary and comprehension?