The report listed the top 20 artists whose music was illegally downloaded, which accounted for some 64.5 million downloads. About 70 percent of the downloads were full albums and 30 percent were individual songs.
Mars' music accounted for 5,783,556 of those downloads, followed by Rihanna, Daft Punk and Justin Timberlake.
Mars was named Billboard's top artist of the year for 2013 after remaining in the top 20 every week since the debut of his album "Unorthodox Jukebox."
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