https://bankenverband.de/media/publikationen/08122015_Zahlen_und_Fakten_V2.pdf
http://www.mckinsey.com/insights/high_tech_telecoms_internet/digital_america_a_tale_of_the_haves_and_hav e_mores?cid=other-eml-alt-mgi-mck-oth-1512