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Power Plays and Penalty Crackdowns

Tracking the effect of the early season crackdown on cross-checking.

Montreal Canadiens v Toronto Maple Leafs
Michael Bunting - drawer of penalties.
Photo by Claus Andersen/Getty Images

This season, there has been a crackdown on cross-checking in preseason. Memos went out to teams explaining what to expect, and there were some preseason games that were awash in penalty time.

This is not the first time the NHL has done this. They did faceoff violations and slashing in the recent past, and if you watch the way the season unfolds, you will see that the PPO (Power Play Opportunities on average per team per game) balloons up, and then comes right back down to normal. But what is normal? It’s not static, that’s for sure, because the amount of penalties called has changed a lot over the years. If you remember the big crackdown on all obstruction penalties coming out of the full lockout and the lost season, you know what the NHL looks like when it comes closer to calling the rulebook.

That year, 2005-2006, is the highpoint for PPO in the modern NHL. What’s happened since? Have a look:

Data from Hockey Reference.

Data is from Hockey Reference, on their league averages page, an invaluable resource for tracking the NHL’s changes over time.

The last bar is this year to date with only 16 games played so far. It is almost one full PPO higher than last season’s lowest ever number.

It’s very easy to get up in arms over the NHL, the refereeing, Gary Bettman personally or (by mistaking his role) George Parros and Player Safety after looking at this chart. The NHL has massive influence on how the games are called, obviously, since they employ the referees and manage them directly. But some of this is likely a fully legitimate decline in infractions committed. Or you better hope it is.

The hope is that enforcement — a crackdown in other words — works. We want some of that decline to be the natural response to that 2005 power play spree, and the changing culture of the NHL that helped to bring about. The trouble with all of this is that we have no idea how many infractions happen in an NHL game and how that has changed. We have no reason at all to believe that PPO is directly related to actual player behaviour. It’s related to referee behaviour, and linking the two is very difficult.

For the NHL, they might point to this same data and claim great success by insisting that refereeing is totally responsive to player behaviour, and this is the proof that their crackdowns were a smashing success. The truth is in the middle somewhere.

What we should expect as the season goes on is to see that final bar drop fairly rapidly back to something like the 2.89 of last season. I’m going to track this every Friday, and we’ll see how much it changes.

Why does this matter if the refereeing is the same overall for every team? And conspiracy theories aside, it likely is. It matters because the NHL is supposed to be an entertaining product and people like goals and scoring chances. Power plays increase the goals scored. Last season there were 2.94 goals on average per game, which is not the lowest ever. The NHL is not that simple a beast to understand. In the period covered in that chart, goals bottomed out in 2003-2004 at 2.57, after a steep decline as the nature of goaltending continued to change. Just 10 years earlier it had been 3.24. The NHL had better players than it had ever had before, and it was boring.

The big boom in PPO after the lockout raised the goals per game back to 3.08, but the decline since has been noticeable. However, skill improvements, changing game styles, the number of teams tanking or operating well below the salary cap and expansion to thin the goalie talent all mix together to give us an ever-changing tension between goals and save percentage in the NHL. Over the last few years, the goals rate has been flirting with 3 most years, even as PPO dropped and save percentage did too.

A few years ago, all anyone could talk about was the size of the nets. The game was getting boring again with a goal rate in 2015-2016 of 2.71, and the goalies were considered to be the culprit by being too big. While the idea to enlarge the nets was a wonderful thing to argue about since it was never going to happen, other influences on save percentage and goal scoring rates need to be considered. The link between save percentage and PPO makes intuitive sense — goalies have a much lower saver percentage shorthanded.

Data from Hockey Reference

Note: for the true believers in an axis that starts at zero, if you do that for save percentage, it’s very difficult to see the changes which are subtle in numerical terms, but we all know the difference in a game between 90% and 92% is extremely significant.

The curve doesn’t match exactly the PPO, but you can see some influence, I think. I looked at this information and marked all the expansion teams once, and there’s a bit of a hint that it plays a role, but it’s not universally true. The most plausible story for the slight decline in save percentage lately is simply a change in the skill balance between the skaters and the goalies. Pick your narrative — is it better defencemen with more offensive skills or is it analytics making teams understand the value of shot location better? Here’s mine: there’s a lot more room for goaltending on average to get worse than there is for it to get better, and the peak at .915 in the two seasons between 2014 - 2016 might just be as high as it can get.

One thing isn’t in doubt, though, PPO going up will increase goal scoring and help make the game a lot more exciting. Will that PPO stay higher? I doubt it. More than just a single-issue crackdown is needed for that to happen.

Next Friday, we’ll meet again and see if that PPO number has come down yet, and what the goals look like.