One of the more disappointing aspects of the hockey stat revolution, if it can even be called that, is that time stops in October 2007. Corsi data goes back no further. Were we to make a graphical representation of our knowledge, we'd have a section labeled October 2007-April 2013 and outside of that would be tigers, griffins, wyverns, and other mythical creatures marking unknown territory. It's a bit of a pin in the balloon of the certainty with which we stat types speak that we have to say things like 'Since 2007-2008...' - I mean, it's a year we all remember pretty well. It's hard to be blown away by anything in that range.
I consider the modern era and thus the Corsi revolution to have begun in around 1995-96. Standup goalies were on the way out, the neutral zone trap was in vogue, and we no longer see teams who win the Stanley Cup with a negative shot differential anymore (like the 80s Oilers). Plus we got 4 more expansion teams which significantly altered one's chances of making the playoffs - before the second round of expansion, 61.5% of teams made the playoffs, now we're down to 53.3%. I just wanted to see how important shots were in a grander scheme than the last six years, so I went all the way back to 1995 and with some hockey-reference finagling, looked at all the non-playoff teams and their shot differentials.
GIANT CAVEAT: I realize that these are loaded up with score effects - teams with poor goaltending are more likely to have good shot differentials because they trail in games more frequently, and teams who miss the playoffs are also likely to be trailing more often. Still, taking a wide view of this data, I think we can still learn a lot from it.
Of the 231 teams to miss the playoffs in the years between 1995 and 2013, 55 had 50% of the shots or better. I didn't run a similar study on the playoff teams to see how many of them had positive shot differentials, but it's pretty clear it's a substantial number. Of those teams who had 50% or better shot percentages and missed the playoffs, 27 of them had made the playoffs the year previous, with an average shot differential of 50.4%, and won an average of nearly 3 playoff games (this counts all teams, whether they made or missed the playoffs, so an average of 3 is pretty good). The 1996 and 2013 Devils, 2003 and 2007 Carolina Hurricanes, 2004 Mighty Ducks of Anaheim, and the 1999 Washington Capitals are six teams who missed the playoffs after having reached the Cup Final the year before, all of whom had shot differentials over 50% the next season. They are also 6 out of the 7 teams who've missed the playoffs after making the Cup Finals the year previous - the other one, the 2006 Oilers, had a positive shot differential the year before their Cup season.
Two teams continually missed the playoffs with a 50+% shot differential - the late 90s Calgary Flames and the late 00s Toronto Maple Leafs. The obvious culprits are terrible goaltending and mediocre shooting - we all know the late 00s Leafs had wretched goaltending in the form of Andrew Raycroft and Vesa Toskala, and the Flames fared no better with a murderer's row of Trevor Kidd, Rick Tabaracci, and Fred Braithwaite.
So how did teams do the season after missing the playoffs with a 50+% shot differential? Not as well as they had done the season before missing the playoffs. Their shot differential is about the same, but only 21 of 52 teams made the playoffs, and all teams only averaged 2.13 playoff wins. However, only 29 teams maintained the 50+% shot differential, and 18 of those made the playoffs. This means that only 3 of the remaining 23 teams who shot worse than 50% made the playoffs the next season. Since poor goaltending is a likely culprit in most of these teams missing the postseason to begin with, it's not that surprising that they couldn't be saved once they fell under the 50% threshold.
I wanted to look at teams with sub 50% shot differentials to see how they do the year after, but I think that is unfortunately mucked up by the fact that this era has a bunch of expansion teams who were pretty likely to struggle for several years. I think we can get by with just Fenwick/Corsi numbers to examine that phenomenon. Regardless, if you have a 50% shot differential or better, you're likely to make the playoffs, and if you didn't make the playoffs with that shot differential, you're likely to make it the next year if you can maintain that level. There's anomalies for sure - the late 90s Flames, the late 00s Leafs, and the 03 and 04 Hurricanes who were particularly ghastly for a team that managed a positive shot differential - but shots are good. Outshooting the other team is good. You tend to make the playoffs if you do it and you tend to miss the playoffs if you don't.