Study: Men are best selling artists by nearly 2-to-1 margin

A study of the best-selling artists in the past five years shows that men outsell women by a nearly 2:1 margin. The data was taken from Nielsen Soundscan numbers, with mixed-gender groups (No Doubt, Black Eyed Peas, etc) removed from the counts. 

“Out of nearly 128.5 million album sales from top-ranked artists every year, 82 million came from men. That's 65 percent, or nearly two out of every three albums sold,” according to Digital Music News, who created the following pie chart to demonstrate:

However, the graph doesn't reflect the latest trend—male versus women sales have become neck and neck in the past two years (credit going to Taylor Swift, Susan Boyle, Lady Gaga and Adele for the shift).

What do you think accounts for the overall disproportionate of sales? Does society lean towards male superstars? Are men putting out more albums in general?