Best selling music artists of all time

Compiling an accurate list has recently become a real headache for modern statisticians with the onset of the digital age. Yet, calculations can be made based on the sum of recorded (hard copy) sales and those of online certified units. Contemporary artist who rely on online sales and video streaming figures can now feature among world's best selling artists. But as you'll see, those names that have been around a while have had the advantage of selling for several decades, as opposed to just several years.
10. Mariah Carey: Approximate sales worldwide: 200 million
9. Eminem: Approximate sales worldwide: 220 million
8. Rihanna: Approximate sales worldwide: 230 million
7. Pink Floyd: Approximate sales worldwide: 250 million
6. Led Zeppelin: Approximate sales worldwide: 300 million
4. Elton John (tied): Approximate sales worldwide: 300 - 350 million
4. Madonna (tied): Approximate sales worldwide: 300 - 350 million
3. Michael Jackson: Approximate sales worldwide: 350 million
2. Elvis Presley: Approximate sales worldwide: 500 million - 1 billion
1. The Beatles: Approximate sales worldwide: 600 million - 1 billion