If you haven’t read my previous write-up on PDO, you probably want to do so now.
When it comes to PDO – loosely rendered as “the combination of shot percentage and save percentage” – there is unfortunately not a hell of a lot of history to work with. It took until the 1983-84 season for shots against to be tracked to any real extent, meaning that calculating save percentages (one-half of the PDO equation) is pretty much impossible. There are people that have gone through old box scores and compiled save percentages from previous years, and these will be used once I get the chance to really get into them.
In the meantime, however, the primary focus is on 1983-84 to 2003-04. And as always, there are a couple big questions that must be addressed when it comes to anything analytical:
- Does it provide a new window into the past?
- Does it have any sort of predictive value?
Each one of these pages will include the goals for and against, shots for and against, shot percentage and save percentage for, and overall PDO. There will also be sections on the playoffs.
Why the playoffs?
PDO is compiled out of regular season statistics, thus providing a window of sorts into the past. But to see if it has predictive value, it’s important to see to what extent PDO correlated with playoff success and specifically individual playoff series.
There exist a handful of what I refer to as “PDO literalists”, who have the idea that because leaguewide PDO has a constant mean (100.00%), and because teams don’t generally deviate from 100% to any extreme, and because the extremes that exist early in a season tend to flatten back toward 100%, that there is an inherent regression to the mean. Therefore, a team that has a PDO of 97% after 80 games has been unlucky and can expect the breaks to start going their way, while a team that has a PDO of 103% after 80 games has been lucky and can expect the breaks to start going against them.
If this theory is true, it should become apparent in the playoffs.
1983-84 to 1990-91: The NHL had 21 teams, with three divisions of five teams and one division of six teams. Each division put their top four into the playoffs, meaning that if one division’s fourth-place team had 65 points and another’s fifth-place team had 91, the one with 65 got in.
1991-92 and 1992-93: In each of these years, the NHL added expansion teams (San Jose in 1991-92, Ottawa and Tampa Bay in 1992-93) while keeping the divisional playoff format.
1993-94 to 2003-04: In each of these years, the NHL had conference playoffs with divisional champions being given an automatic top-2 or top-3 seed (depending on year). The two (1993-94 through 1997-98) or three (1998-99 to 2003-04) division champions in a conference were automatically in, and the remainder of the eight conference playoff spots were filled by the next-best teams in points.
With the division playoffs, the non-playoff teams still tended to be at the bottom of the NHL’s overall standings, but this was not necessarily the case. The issue then was that the lack of competitive balance, and the closed nature of the divisional playoffs, makes a correlative PDO range to playoff appearances extremely difficult to actually pinpoint. With the 2007-08 through 2015-16 seasons, no such difficulty exists.