in f(x)'s defense, download prices increased in 2013 so everyone's sales decreased by a lot. And then when they made their comeback with RPPP, Gaon changed the way they counted Digital Aggregates so their score was WAY lower compared to everyone else's from the last 6-7 months. Their peak was Pinnochio (

), charting at #6 on the year end chart
But their Artpop could mean anything
