There’s some good news and bad news for Justin Timberlake: The good new is his comeback effort, The 20/20 Experience, was 2013’s best-selling album; the bad news is it was the worst-selling best-seller of all time (or, at least since they started keeping track of such things in 1991). Though more than 2 million people bought 20/20, it’s the first time a year’s top-selling record sold less than 3 million copies. As Time points out, the numbers represent a shift in the music industry: Both album sales and digital downloads saw a significant drop in 2013, as more and more listeners are turning to streaming music services like Spotify …