From 2010-2011 through 2013-2014:
2.79, 2.73, 2.72, 2.74
A decline of 1.8% from beginning to end, aka nothing to write home about.
Now look at the scoring leaders. It’s clear there was a bit of a shift in top end scoring that was greater than just league scoring levels, and it wasn’t just because of a lack of talent. PP scoring went down and scoring became more dispersed through the lineup, which continued through 15-16, started raising slightly in 16-17 and then started raising steadily since.