If anyone does sports science for research work, I think there are enough papers out there (like https://rua.ua.es/dspace/bitstream/10045/73710/1/2017_Gonzalez-Rodenas_etal_HumMov.pdf and http://thesportjournal.org/article/analysis-of-goal-scoring-patterns-in-the-2012-european-football-championship/) that you might be able to sift through a whole bunch of them and determine trends over time.

I really just had a gut feeling based on my admittedly limited viewing of mostly goal scoring highlights over the last couple of years. I still think most goals are scored from inside the 18 yard box, but feel like outside 20 yard shots are increasing.