sk any hockey guy and they will all tell you the same thing.
Here's the thing. And I see this a lot which is why I want to address it. I am absolutely sure that if I ask any hockey guy, they will talk about the importance of the things that plus/minus is supposed to measure. And they'd likely be right. But whether or not a particular stat is actually good at measuring it is something way out of their expertise. Just like a pilot might know what he'd need from a plane, but you wouldn't want him to build it. That's not his expertise. In this case, the pilot built the plane. And it keeps crashing.
Here's what plus/minus does measure: The goal differential that occurs while a player is on the ice at even strength, plus the offensive contributions of his team when shorthanded, minus the offensive contribution of the opposing team when on the power play.
So, the first part is borderline useful, even though it needs a lot of context. You have better stats for that though. But why would you credit all players with a plus for scoring a goal shorthanded, when it's often only one player driving it? Why would you completely disregard how they perform at their actual job, which is preventing goals against? Similarly, why would you give everyone a minus for a goal against on the PP, which is often due to a d-man fumbling the puck at the blue line? And why would you be interested in how well a team scores at even strength, but have no interest in how they score at the PP, which is their actual job there?
It's an extremely poorly thought out stat.
Plus/minus correlates to:
1) How strong the team is.
2) What kind of linemates the player has.
3) What kind of usage the player has.
4) Noise. (factors out of the players control)
5) Player impact.
Just to give an example. A large part of the motivation to move out Taylor Hall was driven by plus/minus. The thing is that his plus/minus was only bad due to:
1) Playing on a really bad team who was often behind, so he was often on the ice with the net empty towards the end of the game.
2) Shorthanded goals scored against him on the PP, of which very few came as a result of him in any way.
Without those two factors, Taylor Hall was a plus player on one of the worst teams in the league for many, many years. And that misconception drove one of the worst trades in many years.
I don't think +/- is a bad stat. It's a tool. And like all tools need to be used for the right job.
Sure. The problem with plus/minus is that there is no clear purpose to it as a tool. It tries to be a tool that can do everything, yet is not actually a good choice for anything.