"Did you know, for example, that around 90%..."

"The Bank of English™ forms part of the Collins Corpus. It contains 650 million words from a carefully chosen selection of sources, to give a balanced and accurate reflection of English as it is used everyday" [...]
 
"Did you know, for example, that around 90% of English speech and writing is made up of approximately 3,500 words? Corpus tells us which these words are, and helps us ensure that when you use a cobuild dictionary, you can be sure that you are learning the words you really need to know."


Source: http://mycobuild.com/about-collins-corpus.aspx