Here's an interesting stat.
Look at the season-leading QB ratings of the past 20 years. Since the days of Steve Young and the west-coast offense, the league has had its rating winner at a score of +100 (Young was a freak at pacing the QB rating scores in the league for his entire career, give or take).
Go back in time to the 70s and early 80s, and there maybe 2-4 years every decade where the league's best QB had a rating about 100.
Begs the question: do QBs chase the stat regardless of relevance to winning, or is the stat relevant, and in fact, the league has changed so much in the past 20 years so as to allow freakishly high QB ratings (like Rogers, Manning and Brady in their record-setting seasons).
The stat is weighted to average passing yards per attempt (among other stats, or course).