Average native test-takers of age 8 already know 10,000 words
Average native test-takers of age 4 already know 5,000 words
Adult native test-takers learn almost 1 new word a day until middle age
Adult test-taker vocabulary growth basically stops at middle age
The most common vocabulary size for foreign test-takers is 4,500 words
Foreign test-takers tend to reach over 10,000 words by living abroad
Foreign test-takers learn 2.5 new words a day while living in an English-speaking country