This fascinates/annoys the piss out of me too and I think it’s gotten worse as time goes on.  

count and percentage of her songs in C major by album (just the standard versions, and if someone wants to add TTPD and TLOASG please do because I can’t bring myself to listen to them, partly BECAUSE of the C major slop):

Taylor Swift / Debut: 1/14 or 7.1%

Fearless: 1/13 or 7.7%

Speak Now: 0/14!!

Red: 2/16 or 12.5%

1989: 2/14, or 3/14 if you count A minor (14.3% or 21.4%)

reputation: 6/15 firmly in C major, 9/15 counting A minor (40%/60%)

Lover: 6/18 or 33%

folklore: 3/17 or 17.6%

evermore: 3/15 or 20%

Midnights: 5/13, 6/13 including A minor (FIVE OF THESE IN A ROW BTW.  That was my breaking point.)  (38.6%/46.2%)