I'm talking about the period roughly into the early 2000s. Something happened around that time where NHL reffing got worse, and has progressively deteriorated.
It's backed by evidence. Kerry Fraser has talked some about poor reffing practices over the past decade. Even academia has done research. The UMass-Amherst study that charted 2.6 million shifts over three seasons showed that French-Canadian refs penalize English Canadian players at a significantly higher rate than English Canadian refs. That same study also showed that when two French-Canadian refs are on the ice at the same time English players get called for penalties far more than French players. It's unreal how awful and biased refs are in just that area alone, which isn't even addressing what I'm most concerned with. Research of seasons 2009-2014 showed that refs tend to even out calls as an intentional practice, and perhaps even worse make calls based on score, as teams with the lead get PPs at a rate much lower than the team that is trailing. And of course there is the study done by FiveThirtyEight in which it was shown that over a decade's worth of OT games studied that refs go the extra mile to manage PPs in OT, not calling the penalties that actually occur, but calling penalties based on situation. It's really no big secret that NHL reffing has gotten extremely bad. The eye test certainly can see how rotten it has become on the whole over the past 5 decades, but there is actual research showing how pathetic it has become, and of course plenty of anecdotal evidence from both players and former refs. If the situation, as some suggest, is that the game is just too fast and complex to accurately call, then there would surely be more randomness to what is taking place in terms of penalty calls. Unfortunately research and reality suggest otherwise.