Vinicius Netto asked this question a few days ago. Here is the answer I've found based on a paper by Seto and colleagues.
Proportion of Urban land-cover in km2— Urban Demographics (@UrbanDemog) 22 January 2017
0.5% S America
0.7% N America
2.2% W Europehttps://t.co/qH1aQJrAbG pic.twitter.com/yfKO9Wv6Cz