In the Hockey News, there is a chart of each team's top two goalies pay and below the caption asks the following question: "If goaltending is the most important position in hockey, why do so many of the NHL's bottom-feeders slot up top with their blue ice budgets?".
That is a great question, so I thought that I would use the data on the total salaries each team's top two goalies and compare that with each team's performance, first to see if the idea is on target and to then try to explain these counter-intuitive results.
In order to figure this out, I collected each NHL team's standings data (Games Played (GP), Wins (W), Losses (L), OT, Goals For (GF), Goals Against (GA), Standings Points (PTS)) from nhl.com as of today (January 28th, 2011). Then I included the salary data from the Hockey News (January 31, 2011 edition p. 10) and ran a correlation between standings points and goalie salary. The correlation is -0.2777. Hence the writer is on target saying the teams with higher salaried top two goalies are negatively correlated with standings points at the 2010-2011 NHL All-Star break. As I tell my undergraduate students repeated, correlation does not imply causation. We have to work harder to draw conclusions (i.e. statistical inference) than just calculating the correlation between each NHL team's standings points and the combined salary of the top two NHL goalies on each team. To that I now turn.
In order to make a conclusion using statistical techniques, I decided to employ a linear regression on the data that I collected. The regression that I ran was standings points are a function or are determined by Goals For, Goals Against and Games Played. The result was that each variable is statistically significant (i.e. statistically is different from zero at least at a 95% confidence level) and each variable was of the expected sign. The estimated coefficient on Goals For and Games Played were positive (i.e. more goals for and more games played result in more standings points) and the estimated coefficient on Goals Against was negative (i. e. more goals against results in fewer standings points). Yet, when I then included goalie salary, the estimated coefficient was statistically insignificant (i. e. statistically likely to be zero or not relevant). So we can conclude that salary is not a factor in determining standings points up to the All-Star Break this year. Even if we adjust standings points for the number of games played, there still is no statistically significant relationship between team top two goalie salary and team performance.
OK, so there does not seem to be a statistical link between team top two goalie pay and team performance. What about goals against and salary? Shouldn't teams with higher goalie salaries have lower Goals Against? I would think so, but that is not what I find. I find that the estimated coefficient is negative and statistically insignificant - again meaning that there is no statistical relationship between Goals Against and NHL goalie payroll. Nor do I find a statistical relationship between Wins, Losses and NHL goalie payroll.
All of these findings are consistent with the paper Dave Berri and I published in the Journal of Sports Economics last year. We find that goalie salary and goalie performance are not statistically related. Why? Mainly because goalie performance is highly variable from period to period, game to game and season to season.
This is not a dig at NHL goalies. I think that it is really difficult to find an individual who can game after game consistently stop the puck from entering the net at the NHL level, because doing so against the level of NHL talent is so good, not because NHL goalies are not good. What makes people conclude the opposite is that they focus on those goalies (such as Martin Brodeur or Dominic Hasek) who for many years perform at an above average level, they they believe that all goalies can do so. If we look at Brodeur's stats this year, we see that he is (using our NHL goalie measure of Wins Above Average) is only better than Brian Elliott, Dan Ellis and Nikolai Khabibulin.
That leaves us with the conclusion, that if goalies performance is highly variable, NHL GM's should spend more of their capped payroll on other positions and hope for the best at the goalie position.
No comments:
Post a Comment