1 Answer

From WIKIPEDIA:

The list of best-selling music artists includes artists with claims of 75 million or more record sales in multiple third-party reliable sources. The claimed sales figures and the total certified sales figures (for each country) within the provided sources include sales of albums, singles, compilation-albums, music videos as well as downloads of singles and full-length albums. The artists in the following tables are listed with both their claimed and certified sales figures and are ranked in descending order, with the highest claimed sales at the top. Artists with the same claimed sales are then ranked by certified units. Sales figures, such as those from Soundscan, which are sometimes published by Billboard magazine, have not been included in the certified units column. Currently, The Beatles are listed at the top of the list as they are considered the highest-selling band based both on sales claims and certified units. Elvis Presley, who is listed the second on the list is considered the highest-selling individual artist based both on sales claims and certified units.
All artists included on this list, which have begun charting on official albums/singles charts have their available claimed figure(s) supported by at least 20% in certified units. That is why Cliff Richard, Diana Ross, Charles Aznavour, Bing Crosby, Nana Mouskouri, Deep Purple, Iron Maiden, Tom Jones, The Jackson 5, Dionne Warwick, The Andrews Sisters, Luciano Pavarotti and others have not been included on this list. The percentage amount of certified sales needed increases the newer the artist is, meaning, artists such as Taylor Swift and Rihanna are expected to have their claimed figures supported by over 60% in certified units. The certified units are sourced from available online databases of local music industry associations. Note that all certified units are converted from Gold/Platinum/Diamond certification awards based on criteria provided by certifying bodies.
The requirements of certified sales are designed to avoid inflated sales figures, which are frequently practiced by record companies for promotional purposes.[1][2]
The claimed figures are sourced to articles that use the term records (singles, albums, videos) and not albums. However, if all available sources for an artist/band say albums, such sources can only be used if the certified album units of the said artist meet the required percentage amount. Note that this list uses claimed figures that are closer to artists' available certified sales. In other words, inflated claimed figures that will meet the required certified sales amount but are unrealistically high from available certified