By Antonio Papa
This season, the NHL has initiated a rule change to create more overtime goals and fewer shootouts. Now, overtime play will be 3-on-3, instead of 4-on-4. A quick statistical analysis shows us that the new rule has – and will continue to – increase overtime scoring.
Shootouts were added after the 2005-06 lockout as an alternative to ties in the regular season, but they have been criticized as essentially flipping a coin to decide the winner. 3-on-3 play, in contrast, gives stronger teams an increased chance of scoring goals. In the early 1980s, the Edmonton Oilers even told their defenders to get into mutual roughing penalties on purpose so that the game would become 4-on-4 or 3-on-3. Then, Wayne Gretzky, Jari Kurri and Mark Messier would take over on the open ice. This was effective because players with superior skating ability gain an upper hand in 4-on-4 and 3-on-3 situations, resulting in more goals scored.
The NHL instituted the “Gretzky rule” in 1985 as a direct response to these shenanigans. The “Gretzky Rule” created the concept of coincidental minor penalties and allowed full strength play for offsetting penalties. A few years later, the NHL reversed the change in an attempt to reclaim some of that high-scoring open play. Expect this year’s 3-on-3 overtime to benefit top-heavy teams, like the Pittsburgh Penguins, who are sure to take advantage of the situation with skaters like Sidney Crosby, Evgeni Malkin and Phil Kessel.
Over the past eight seasons, 43% of overtime games had a goal and the other 57% needed a shootout (2,227 games). In this preseason’s overtime games with the rule change in place, 72% of overtime games had a goal and only 28% needed a shootout (24 games). Even with the small sample size, we can use a T-test (difference of means) to determine whether this change is statistically significant. The standard binomial error is σ = .0105 for the regular season set and σ = .0926 for the preseason set. The result is that we are 99% confident that the new rule decreases the proportion of shootouts in overtime by 40%-58% (about half) and should lead to high-octane teams winning more games in overtime.
[Editor’s Note: The last paragraph was edited post-publication to clarify the statistical test used]