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Advanced Metrics: How useful is raw +/-?

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You can't put too much stock in to plus-minus, here's why:

Jim McIsaac

Someone asked friend of the blog Neil Greenberg how reliable individual +/- is. I think it's very reliable - in fact, you would do reasonably well signing the player who finishes dead last in the league in +/- every season provided he wasn't on an expansion team. Let's take a look at that list:

Season Player GP +/- GP Year2 +/- Year 2
2010-11 Chris Phillips 82 -35
2009-10 Patrick O'Sullivan 73 -35 31 4
2008-09 Brendan Witt 65 -34 42 -18
2007-08 Radek Bonk 79 -31 66 -12
2006-07 RJ Umberger 81 -32 74 0
2005-06 Mark Recchi 83 -36 82 1
2003-04 Rico Fata
73 -46 no season no season
2002-03 Jay Bouwmeester 82 -29 61 -15
2001-02 Tyler Wright 77 -40 70 -25
2000-01 Patrice Brisebois 77 -31 71 9
1999-00 Yannick Tremblay 75 -42 46 -6
1998-99 Darcy Tucker 82 -34 77 -12
1997-98 Paul Ysebaert 82 -43 10 -5
1996-97 Alexandre Daigle 82 -33 75 -8
1995-96 Owen Nolan 81 -33 72 -19
Craig Janney 84 -33 77 -1
1994-95 Chris Dahlquist 46 -30 24 -7
1993-94 Gord Dineen 77 -52 9 -5
1992-93 Rob Zettler 80 -50 42 -7
Doug Zmolek 84 -50 68 -9
Neil Wilkinson 59 -50 72 2
1991-92 Paul Fenton 60 -39 retired retired
1990-91 Michel Petit 73 -34 70 -15
1989-90 Bryan Fogarty 45 -47 45 -11
1988-89 Tom Fergus 80 -38 54 -18
Average 74 -38 56 -8

More than half of these guys were in the middle of otherwise fine NHL careers and found themselves getting a lot of tough ice time on an awful team and, on top of that, had all of the bounces go against them. The top half of these players went from an average of 74 GP and -38 in their bad +/- season to 73 games and a -7 in their next season.

This relates back to our discussion of PDO on Friday. A lot of bad +/- is driven by a low on-ice shooting percentage and a low on-ice save percentage - PDO. And PDO has zero year-to-year correlation, so it's difficult to infer much skill from a bad +/-. And clearly a lot of decision-makers in the NHL do get that (otherwise they'd cut their +/- trailers) but I'm willing to bet that guys with poor +/- are still undervalued.