If you were watching anything music-related on YouTube last year, there's a good chance it was Katy Perry. Her channel was the most-watched on the video site among musicians, pulling in nearly 2.4 billion views last year. Yes, billion. She was also the third-most watched channel over all across the site. So this whole Super Bowl halftime thing totally makes sense. Three of her videos alone — "Dark Horse," "This Is How We Do" and "Birthday" — were responsible for 1.2 billion of those views. Yikes. Don't kids listen to mp3s anymore?
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