Top 50 certified best-selling artists of all time

Guess who are the top 50 certified best-selling artists of all time (only *certified* units sold from available markets). Source: WIkipedia. Please note: Certification databases are not a definitive indication of the actual sales worldwide. Some records released prior to a certification system's establishment year (which are different in each available country) may not be found within the available searchable certification databases. This basically means that data-wise recent artists are favoured in terms of album sales numbers, so bear this in mind!