Sports Reference Blog

SV%+ Calculation Poll

Posted by Neil on October 10, 2013

In case you missed it yesterday, we rolled out a couple of new goaltending stats for the 2014 season -- Save Percentage+ and Goals Saved Above Average. Overnight we got some feedback about SV%+ in particular, and the structure of having 1 minus the goalie's own SV% in the denominator of the formula. Right now, we are measuring the rate at which the league allowed more goals than the player, where 100 = average. So in the case of a 133 SV%+, the league's rate of goals allowed per shot would be 33% higher than the player's rate.

There are other alternatives. If we re-arrange the formula so that 1 minus the league SV% is in the denominator, we would be measuring the rate at which the player allowed fewer goals than the league. (Because of the nature of division, this is an important distinction from the definition in the previous paragraph.) If we tweak the formula in this direction, there are 2 options: we can compute a "minus" type of stat in which lower numbers are better, or we can stick with the "plus" style familiar to all from baseball's OPS+ and ERA+. The former would represent a goalie who allows 33% fewer goals than the league as a 67 (remember, lower is better); the latter would represent that as a 133.

(If any of this sounds familiar, it's because this battle was fought at Baseball-Reference 3 years ago and continues to rage in some corners of the internet to this day.)

As is the case sometimes in this business, there is no "right answer" here, but rather a matter of preference. For instance, we've long assumed users would find it counterintuitive to have a rate stat where lower numbers = better performance, but maybe that's not true. I'm interested in opinions on this, so let your voice be heard in the following poll -- which format do you prefer? Or do you care at all? I can't promise the poll-winning format will be what we eventually stick with, but I'd like to know what people think.


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This entry was posted on Thursday, October 10th, 2013 at 2:09 pm and is filed under Announcement, Hockey-Reference.com, Polls, Stat Questions. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

7 Responses to “SV%+ Calculation Poll”

  1. Bill Says: October 10th, 2013 at 5:40 pm

    Save% is a higher=better stat. Save%+ should be how it is now.

    GAA+ would be where you would want a golf score number.

  2. Ty Says: October 10th, 2013 at 6:42 pm

    I agree with Bill. Also, it would be great if you could separate Save%+ from Even Strength (and differentiating between 5-on-5, 4-on-4, and the rare 3-on-3), and Man-Advantage. Some goalies would be unfairly penalized because their team commits more penalties, compared to other teams.

  3. Tangotiger Says: October 10th, 2013 at 8:20 pm

    I agree that save percentage is higher is better.

    Except what will be shown is based on the % of goals allowed. He's doing 1-SV%, which is the same thing as goals per shot.

    SV%+ is therefore a misnomer. Hasek is not saving 149% of the league average. The league is allowing goals at 149% of Hasek.

    Or, Hasek is facing 149% of the shots the league is facing, for every goal allowed.

  4. Tangotiger Says: October 10th, 2013 at 8:49 pm

    As an example, imagine you have fielding percentage for baseball, and it'll be shown as FLD%+. But it'll be calculated as Errors/Chances. Imagine that your fld% is .990 and the league average is .970. These are your three choices:

    300
    167
    33

    None of that is about FLD%. They are all based on Error Rate.

    Option 1 says: "League makes an error at 300% relative to this player"
    Option 2 says: "Player makes an error 67% less than the league"
    Option 3 says: "Player makes an error at 33% of the league rate"

    And the title of the metric couldn't be FLD%+, but ERR%+.

    Goals Allowed would be the analogy to errors, and shots to chances.

  5. Greg Ralls Says: October 11th, 2013 at 12:42 pm

    I don't have a preference so I chose the "don't care" option. I didn't want that to be mistaken as apathy, though. I love having more stats available, and am thrilled with this addition to Hockey-Reference.

  6. Tangotiger Says: October 11th, 2013 at 3:44 pm

    Right, "Don't care" is really "In some form, as long as it's there".

  7. Doug Norris Says: October 15th, 2013 at 4:42 pm

    Hi guys - I think that either the current way or New Way #1 works equivalently (although GSAA duplicates one unless I'm understanding it not properly).

    Have you considered a replacement-level metric? There's definite positive value to being average.

    On my site, I do both GD (goal differential, which appears to be an analog to GSAA) and GAR (goals above replacement, which compares to a goaltender with a save percentage 0.015 below league average - something I arrived at empirically).

    For instance:
    http://hockeygoalies.org/bio/roy.html
    http://hockeygoalies.org/bio/hasek.html
    http://hockeygoalies.org/bio/brodeurm.html

    (under REGULAR SEASON STATISTICS)

    I describe it more here:
    http://hockeygoalies.org/stats/glossary.html

    Anyhow, just something to think about - I love that sites like this are developing more advanced ways of looking at goaltenders' performance.