hockey stats

The NHL has gone through several somewhat major rule changes over the years, which makes it somewhat difficult to compare players and teams across eras. So here's my attempt at rectifying this.

From the beginning of the NHL up to and including the 1998-99 season, points were awarded as follows:
Win in regulation - 2 points
Loss in regulation - 0 points
Win in overtime - 2 points
Loss in overtime - 0 points
Tie - 1 point

This meant that for every game, 2 points were awarded. So the number of points in the standings was (# of teams) * (# of games in the season)

From the 1999-00 season until 2003-04 season, points were awarded as:
Win in regulation - 2 points
Loss in regulation - 0 points
Win in overtime - 2 points
Loss in overtime - 1 points
Tie - 1 point

The difference is the point for an overtime loss. The idea was that teams were playing for a tie in overtime rather than risk earning nothing, so they gave both teams a point going into overtime, then if someone scored they got another point. What this did was increase the number of points in the standings, making it (# of teams) * (# of games in the season) + (# of games won in overtime). More than adding points, this also added variation to the number of points each season, leading to different playoff qualifying situtaions each year.

Since 2005-06, the scoring is:
Win in regulation - 2 points
Loss in regulation - 0 points
Win in overtime - 2 points
Loss in overtime - 1 points
Win in shootout - 2 points
Loss in shootout - 1 points

Ties are eliminated, so every overtime game will yield 3 points. Since shootout wins and overtime wins are identical from a points perspective, I'll just refer to both of these as OT wins. So the number of points in the system is (# of teams) * (# of games in the season) + (# of games going to overtime). We still have variation and an even larger number of points than the other two settings.


So who was better, the 05-06 Red Wings with 124 points, 01-02 Red Wings with 116 points, or 97-98 Stars with 109 points?? (These are arbitrary comparisons)

One option is to look at the ratio of points earned to the average # of points a team earned in those 3 years.

97-98 teams averaged 82, ratio is 1.33
01-02 teams averaged 86.03, ratio is 1.35
05-06 teams averaged 91.47, ratio is 1.36

We can alternatively look at the number of standard deviations each is away from the mean:
97-98 Stars - 1.71
01-02 Red Wings - 1.995
05-06 Red Wings - 1.976

The 109 points is clearly not quite as impressive, but the 116 and 124 look very close. The ratios are nearly identical, with the 116 being more SDs away from the mean, largely due to the increase in variance in points under the current system. Of course, the evidence is really telling us that 116 in 01-02 is roughly equivalent to 124 in 05-06 (or any year in today's system). So always be weary of comparing team points without acknowledging the system under which it was obtained.

So what does it mean for this season?? Well last year 22.8% of games went to OT. So far a sixth of the way into this season, only 13.9% of games are going to OT. So instead of 2741 points last year, we're on pace for 2631 points, which is only slightly more than we saw in the previous points system. If this keeps up (I don't have game by game data to see if this is possibly a typical early season trend), expect teams to need fewer points to reach the playoffs. Instead of 93.75 (the average in the past 2 years), a team might need only 90.

Of course if Ottawa keeps hogging all the points, things could change.

The other implication of the new system is on goalie stats, but that will need to wait for another post.