How large a vocabulary is needed for reading and listening?

This article has two goals: to report on the trialling of fourteen 1,000 word-family lists made from the British National Corpus, and to use these lists to see what vocabulary size is needed for unassisted comprehension of written and spoken English. The trialling showed that the lists were properly sequenced and there were no glaring omissions from the lists. If 98% coverage of a text is needed for unassisted comprehension, then a 8,000 to 9,000 word-family vocabulary is needed for comprehension of written text and a vocabulary of 6,000 to 7,000 for spoken text.