Stats: What happened in 2013?

As most of you know, the members of Denniz Pop’s old studio and their mentees basically run the pop world (Rami Yacoub, Max Martin, Shellback, Luke, etc.)

So I decided to do some research and see just how much Denniz’s legacy producers and writers have dominated the Billboard T10. Here are the results for this decade:

2010: 12/60 = 20% of all songs
2011: 12/54 = 22% of all songs
2012: 14/50 = 28% of all songs
2013: 4/52 = 8% of all songs
2014: 7/50 = 15% of all songs
2015: 8/35 = 23% of all songs

It seemed like they were doing extremely well in the beginning of the decade (due to Luke’s work with Kesha and Perry, Yacoub with One Direction, and Max with random people) but then in 2013 they only produced 4 top ten hits TOTAL out of 52 top tens. They’ve recovered since then (largely thanks to Max’s work with Ariana and Taylor) but what happened in 2013? Did pop music just die to Indie that year or what?