Special Teams Shot Differential

Mike 'Doc' Emrick purports to hate numbers and mentions how bad he is with them, but one of the numbers he liked and mentioned often during his regular broadcasting days was something called Special Teams Index - it was quite basic, you summed a team's power play percentage and a penalty kill percentage, and voila - there was your Special Teams Index. 100 is average, anything 5-10+ points above is real good, anything 5-10+ points below is real bad. Easy stuff, right?

These days, we know a bit better - we know that penalty killing and power play success is driven by the number of shots a team is able to both get and prevent and that teams don't have a huge amount of control over either shooting percentage or goaltending. Furthermore, power play and penalty killing percentage don't take into account how many short handed goals a team either allows or scores, much less shots. So knowing that shots tend to be more meaningful than goals when we think about what's going to happen in the future, I whipped all these new items into something I call Special Teams Shot Differential - It's the sum of a team's power play shot differential (Shots For per 60 minutes - Shots Allowed per 60 minutes) and penalty killing shot differential. Here's a table of the whole league, with their 5v4 and 4v5 goal differentials on beside it (numbers courtesy of behindthenet.ca, which is updating wonkily and thus these numbers may be slightly incorrect).

Team	Shot Differential	Goal Differential
PHI	17.9	8
ANA	17.5	-3
BOS	12.9	6
STL	13.1	4
NJD	12.2	2
OTT	6.8	7
LAK	6.5	4
SJS	6.0	8
CBJ	3.7	4
NYI	3.6	8
PIT	2.6	0
MTL	2.5	6
MIN	2.2	0
NSH	1.9	-7
TOR	1.3	3
DET	0.3	-4
FLA	-0.2	-2
PHX	-0.9	-2
CHI	-1.1	0
WPG	-2.3	-7
CGY	-3.9	4
CAR	-7.6	-11
VAN	-8.3	-11
COL	-9.1	-9
NYR	-10.3	-7
DAL	-11.1	0
BUF	-11.5	-15
EDM	-12.2	12
TBL	-13	-3
WSH	-17.6	4

Now I haven't included power play differential in this at all, so some things will be skewed - some teams who are close to 0 in shot differential may be generating more shots than they allow by virtue of drawing more penalties and vice versa. Still, we see the teams who have a bad shot differential tend to give up goals on special teams, and teams who have good shot differentials score them. Most surprising on this list to me was Anaheim, who've led a charmed existence at even strength but are really quite good on special teams and are not fully seeing the benefits of that (Their -26 PP/PK differential is the culprit here - ditto Boston, who's having a remarkable year on the PK). Still, though, we see just how little 5v4 and 4v5 power plays and penalty kills matter in the big picture - few teams have a differential plus or minus 10, those that do are largely driven by luck, and we're nearly halfway done with a regular season.