Thursday, March 22, 2007

East vs. West

One argument being used in favour of Eastern goaltenders this year is that it is tougher to play there. The main justification for this is that 15 of the top 20 goalscorers currently play in the Eastern Conference, led by players such as Lecavalier, Ovechkin and Heatley. If the top talent is in the East, then it follows that goalies such as Brodeur, DiPietro, et al. have a harder job than their counterparts out West.

On the surface, this seems to be correct. Looking at goals per game, Eastern teams average 3.0 goals for and 3.0 goals against per game, while Western teams average 2.8 goals for and 2.8 goals against. This means that there is 0.4 more goals per game in games involving Eastern teams.

However, we need to try to find out why this is, before rushing to attribute it to the shining talents of Crosby, Ovechkin, and company. There are six major reasons why goals would be higher in one conference than in the other: more shots, more dangerous shots, better shooters, more/less penalties, better special teams, and worse goalies. Let's look at them one by one:

Although I have heard worse goalies used as a justification, this one does not appear to hold water. Seven of the top 15 goalies in shot-quality neutral save percentage (courtesy Hockey Numbers) are from the East. With DiPietro, Huet, Lundqvist, Lehtonen, Brodeur and Kolzig, the East is not lacking in goalie talent. Looking at the top 10 in SQNSV% in each conference (West .910, East .908), it appears the West has a slight edge, but it is pretty close. Based on the average of 30 shots per game, this accounts for a difference of 0.1 goals per game.

The difficulty of shots taken is not easy to measure, and we must rely on statistical measures of shot quality to estimate it. According to one model (Hockey Numbers), even-strength shot quality in the West has been 0.98, in the East 0.99. Again, essentially the same (1% difference), and certainly not enough to justify the difference in scoring.

Better shooters is the most common explanation. This, however, is not supported by the evidence. The shooting percentage for Eastern teams is 9.8%. For Western teams it is 9.7%, which is very close. This difference of 1% can be entirely explained by the 1% difference in shot quality. Therefore, the East is not any better at scoring than the West. If anything, the opposite appears to be true, given that Western goalies are a little bit better.

There is not much difference in penalties taken either. Western teams have been shorthanded on average 361 times this season. Eastern teams have averaged 359 times shorthanded, which is a difference of .01 times per team per game.

Looking at special teams, Eastern teams have been successful on 17.8% of their power plays, Western teams only 17.5%. This small edge is counteracted by the difference in penalties taken, meaning the difference between East and West in power play goals scored is all of 4 goals.

Having dismissed five of the six factors, we turn to the last one, shots taken. Finally, here is something to take note of: Western teams average 29.1 shots for and 28.7 shots against, for a total of about 58 per game. Eastern teams average 30.2 shots for and 30.7 shots against, for a total of about 61 per game. This is a difference of 3 shots per team per game, or 5%. Given the league average scoring rate, this accounts for a difference of 0.3 goals per game, which is nearly the entire gap between East and West. The difference, it would seem, is in the style of play between the two conferences - the East tends to be more open, allowing for more shots to be taken. Western teams play more of a closed game, and are more effective at preventing shots.

Having looked at the difference for the conferences as a whole, let's turn to the top talent. Is it justifiable to claim that 75% of the league's top scorers reside in the Eastern Conference? Or are lurking variables again clouding the analysis? Evidence suggests that indeed they are, and again it is shots taken that is the prime culprit.

Of the top 20 goalscorers, 15 play in the East. These 15 players have averaged 257 shots on goal so far this season. The remaining 5 are from the West. If the difference was talent, then they would be expected to have a similar average number of shots. They do not - the 5 players have averaged only 216 shots, or 41 less than the Eastern shooters.

This is a little unfair to compare the top 5 to the top 15, so let's look at the averages for the top 10 scorers from each conference:

East: 39 goals on 265 shots, 14.7% shooting
West: 33 goals on 210 shots, 15.7% shooting

This shows clearly that the difference is not talent, but simply opportunity. The top goalscorers are found in the East because they simply take more shots. The West's best shooters have actually been more effective at scoring on the shots they have taken. There is of course skill involved in creating shots, which can be attributed to the top players in East. Eastern teams, however, also tend to rely on their best players a little more. The top 10 scorers in the East average about 1 minute more per game on the ice at even strength, and half a minute more on the power play. This helps to further explain the difference in scoring.

In conclusion, claims that the league's best shooters can be found in the Eastern Conference appear to be largely overblown. Eastern Conference players have scored more goals because they take more shots than their Western counterparts, but their scoring efficiency is not any better. They are more effective at creating shots, but this is mitigated by increased ice time as well as the overall conference statistics indicating that Eastern games are more open and have more shots taken.

In terms of ranking goalies, conference effects can be almost completely disregarded. The only significant differences for the goal differential were shots taken and goaltending play. Shots do not affect the best goaltending measures such as save percentage. For other statistics, goalies should be judged based on the teams they play behind, which has much more of an impact. For example, New Jersey and Tampa Bay allow a relatively low number of shots against, despite playing the "wide-open" East, while Phoenix and Nashville allow a high number of shots, despite playing in the "defensive" West. Therefore, there is no reason to claim a conference effect is discriminating against goalies in either the East or the West, since individual team effects are much more significant.