Comparing Book Vocabulary, Rapper's Influence, and Charity Giving

It's a 'fact' beloved of English teachers around the world: that Shakespeare, the greatest playwright in English, also had the greatest vocabulary. But research published earlier this year suggests English teachers might have to look elsewhere to establish the superiority of the Bard - apparently his vocabulary lags behind the best and most famous rappers of the last decades. Is this comparison fair, and if so, does it diminish the Bard's lustre? This programme was first broadcast on the BBC World Service.