Turns out it's harder than you think.
Threshold save percentage (Spt) is defined in terms of average save percentage. There is a typo in the equation in the article at this point. Let me define Yield (Y) as Y = 1 – SP. Threshold yield Yt is defined as 4% more than average yield, or Yt = Ya * 1.04. Thus, SPt = SPa - GTV * (1 - SPa)
|
Save Percentage |
ES |
PK |
PP |
Total |
|
Average |
0.917 |
0.868 |
0.914 |
0.909 |
|
Threshold |
0.914 |
0.863 |
0.911 |
0.904 |
Expected goals are calculated as shots faced times save percentage. Expected goals minus actual goals gives GGVTraw. This is then multiplied by 0.75 to get GGVT. Two additional components, for puck-handling and shootout are added to GGVT to get total GVT. I'm not going to calculate these, but they are small relative to GGVT. Seems easy enough, but I'm not getting the same values Gabe has in his tables. I calculated a piece of GGVTraw at ES, another on PK, and a third on PP. These are added up. For example, for Ryan Miller, I get expected goals against as 197.06, GGVTraw of 47.06, and GGVT as 35.3. Gabe's tables have it as 38.5. Similarly, for Vesa Toskala I get GGVTraw as -18.75 and GGVT as -14.1. Gabe's tables have him at -13.8. In fact, my calculated GGVT values average 1.12 less than Gabe's tables. The appendix has the calculated GGVT values for 2009.
I then calculated GGVT based on total shots and total save percentage. Miller 38.56, Toskala -14.1. Still not quite right. These values are low by 0.51 on average. The appendix also has these values.
I'm going to declare victory and move on. I'm going to calculate GGVT a piece at a time, ES plus PK plus PP. I'll call what I calculate GGVT* to make it clear that what I am calculating is not quite GGVT, although the difference is small, much smaller than the standard deviation we saw with GVA. I suspect the difference in GGVT and GGVT* reflects a difference in calculating shot mix.
Acknowledgment
I want to thank Tom Awad for his patient and very helpful correspondence about GVT.
Appendix
GVTcalc : the GVT calculated from ES + PK + PP
GVTact : GVT from Gabe's tables
Diff1 : difference between GVTcalc and GVTact
GVTtot: the GVT calculated from total shots
Diff2 : the difference between GVTtot and GVTact
|
Name |
GVTcalc |
GVTact |
Diff1 |
GVTtot |
Diff2 |
|
MillerRyan |
35.30 |
38.50 |
-3.20 |
38.56 |
0.06 |
|
VokounTomas |
29.29 |
31.50 |
-2.21 |
32.08 |
0.58 |
|
NabokovEvgeni |
28.28 |
30.50 |
-2.22 |
28.60 |
-1.90 |
|
HowardJimmy |
24.95 |
26.80 |
-1.85 |
27.38 |
0.58 |
|
BryzgalovIlya |
24.06 |
26.00 |
-1.94 |
24.91 |
-1.09 |
|
KiprusoffMiikka |
23.97 |
25.70 |
-1.73 |
24.19 |
-1.51 |
|
LundqvistHenrik |
23.66 |
28.30 |
-4.64 |
24.27 |
-4.03 |
|
RaskTuukka |
23.23 |
24.90 |
-1.67 |
26.60 |
1.70 |
|
AndersonCraig |
20.15 |
21.90 |
-1.75 |
21.04 |
-0.86 |
|
HalakJaroslav |
19.26 |
21.70 |
-2.44 |
21.28 |
-0.42 |
|
HillerJonas |
18.53 |
20.90 |
-2.37 |
19.92 |
-0.98 |
|
BrodeurMartin |
13.54 |
17.10 |
-3.56 |
18.29 |
1.19 |
|
WardCam |
12.20 |
13.10 |
-0.90 |
12.20 |
-0.90 |
|
LuongoRoberto |
11.60 |
14.50 |
-2.90 |
10.01 |
-4.49 |
|
MasonChris |
11.53 |
13.80 |
-2.27 |
11.31 |
-2.49 |
|
HedbergJohan |
11.21 |
12.30 |
-1.09 |
8.30 |
-4.00 |
|
ConklinTy |
10.40 |
10.90 |
-0.50 |
11.33 |
0.43 |
|
TurcoMarty |
10.00 |
10.60 |
-0.60 |
12.63 |
2.03 |
|
LaBarberaJason |
8.41 |
8.70 |
-0.29 |
10.56 |
1.86 |
|
ThomasTim |
8.37 |
9.60 |
-1.23 |
9.91 |
0.31 |
|
PriceCarey |
6.87 |
8.40 |
-1.53 |
4.01 |
-4.39 |
|
TheodoreJose |
6.41 |
7.40 |
-0.99 |
7.82 |
0.42 |
|
NiittymakiAntero |
6.08 |
6.10 |
-0.02 |
3.77 |
-2.33 |
|
RinnePekka |
5.56 |
7.70 |
-2.14 |
5.89 |
-1.81 |
|
NiemiAntti |
5.38 |
6.00 |
-0.62 |
6.59 |
0.59 |
|
ElliottBrian |
5.22 |
6.60 |
-1.38 |
2.71 |
-3.89 |
|
BrodeurMike |
4.13 |
4.10 |
0.03 |
4.69 |
0.59 |
|
BernierJonathan |
3.64 |
3.80 |
-0.16 |
3.79 |
-0.01 |
|
BudajPeter |
3.02 |
3.90 |
-0.88 |
2.90 |
-1.00 |
|
KhudobinAnton |
2.81 |
2.70 |
0.11 |
8.20 |
5.50 |
|
ClemmensenScott |
2.73 |
3.70 |
-0.97 |
5.03 |
1.33 |
|
NeuvirthMichal |
2.72 |
3.60 |
-0.88 |
3.41 |
-0.19 |
|
QuickJonathan |
2.69 |
5.50 |
-2.81 |
3.85 |
-1.65 |
|
DanisYann |
2.44 |
2.80 |
-0.36 |
2.48 |
-0.32 |
|
GiguereJean-Sebastien |
2.36 |
2.80 |
-0.44 |
1.95 |
-0.85 |
|
EllisDan |
2.11 |
2.90 |
-0.79 |
1.47 |
-1.43 |
|
GreissThomas |
1.99 |
2.80 |
-0.81 |
2.29 |
-0.51 |
|
RaycroftAndrew |
1.98 |
2.90 |
-0.92 |
0.50 |
-2.40 |
|
PavelecOndrej |
1.85 |
2.50 |
-0.65 |
0.19 |
-2.31 |
|
VarlamovSemyon |
1.84 |
3.70 |
-1.86 |
0.27 |
-3.43 |
|
LehtonenKari |
1.83 |
1.90 |
-0.07 |
0.23 |
-1.67 |
|
KhabibulinNikolai |
1.58 |
2.20 |
-0.62 |
1.10 |
-1.10 |
|
RolosonDwayne |
1.49 |
3.40 |
-1.91 |
2.09 |
-1.31 |
|
FleuryMarc-Andre |
1.41 |
3.90 |
-2.49 |
2.95 |
-0.95 |
|
JohnsonChad |
1.24 |
1.60 |
-0.36 |
3.31 |
1.71 |
|
LalimePatrick |
1.20 |
1.10 |
0.10 |
0.35 |
-0.75 |
|
LegaceManny |
0.84 |
2.50 |
-1.66 |
2.23 |
-0.27 |
|
EmeryRay |
0.61 |
2.10 |
-1.49 |
-0.35 |
-2.45 |
|
ErsbergErik |
0.60 |
0.60 |
0.00 |
-0.46 |
-1.06 |
|
LeightonMichael |
0.40 |
2.00 |
-1.60 |
-0.34 |
-2.34 |
|
SchneiderCory |
0.33 |
0.50 |
-0.17 |
0.10 |
-0.40 |
|
JohnsonBrent |
0.24 |
1.30 |
-1.06 |
1.89 |
0.59 |
|
CrawfordCorey |
0.20 |
0.20 |
0.00 |
0.70 |
0.50 |
|
PechurskiAlexander |
0.20 |
0.20 |
0.00 |
-1.10 |
-1.30 |
|
BacklundJohan |
0.17 |
0.20 |
-0.03 |
-1.30 |
-1.50 |
|
McElhinneyCurtis |
-0.13 |
2.90 |
-3.03 |
-1.01 |
-3.91 |
|
ZabaMatt |
-0.24 |
-0.30 |
0.06 |
0.88 |
1.18 |
|
PetersJustin |
-0.31 |
0.30 |
-0.61 |
-0.59 |
-0.89 |
|
EnrothJhonas |
-0.41 |
-0.40 |
-0.01 |
-1.62 |
-1.22 |
|
DuchesneJeremy |
-0.45 |
-0.40 |
-0.05 |
2.17 |
2.57 |
|
GaronMathieu |
-0.54 |
0.60 |
-1.14 |
-0.53 |
-1.13 |
|
HardingJosh |
-0.56 |
0.50 |
-1.06 |
-1.45 |
-1.95 |
|
TokarskiDustin |
-1.18 |
-1.10 |
-0.08 |
0.98 |
2.08 |
|
DubielewiczWade |
-1.21 |
-1.20 |
-0.01 |
3.74 |
4.94 |
|
ClimieMatt |
-1.22 |
-1.00 |
-0.22 |
-2.06 |
-1.06 |
|
DipietroRick |
-1.30 |
-0.30 |
-1.00 |
0.32 |
0.62 |
|
SalakAlexander |
-1.41 |
-1.60 |
0.19 |
3.21 |
4.81 |
|
MacDonaldJoey |
-1.42 |
-1.40 |
-0.02 |
-0.47 |
0.93 |
|
CurryJohn |
-2.16 |
-2.70 |
0.54 |
1.58 |
4.28 |
|
GustavssonJonas |
-2.56 |
-1.20 |
-1.36 |
-5.03 |
-3.83 |
|
BackstromNiklas |
-3.26 |
0.40 |
-3.66 |
-1.49 |
-1.89 |
|
BoucherBrian |
-3.69 |
-1.40 |
-2.29 |
-2.69 |
-1.29 |
|
MasonSteve |
-3.99 |
-1.50 |
-2.49 |
-4.90 |
-3.40 |
|
BironMartin |
-4.40 |
-4.70 |
0.30 |
-4.08 |
0.62 |
|
ValiquetteSteve |
-4.96 |
-4.80 |
-0.16 |
-1.00 |
3.80 |
|
SmithMike |
-5.07 |
-2.60 |
-2.47 |
-6.31 |
-3.71 |
|
AuldAlex |
-5.24 |
-3.80 |
-1.44 |
-3.87 |
-0.07 |
|
DeslauriersJeff |
-5.32 |
-3.60 |
-1.72 |
-3.23 |
0.37 |
|
DubnykDevan |
-6.31 |
-6.20 |
-0.11 |
-3.91 |
2.29 |
|
OsgoodChris |
-7.86 |
-6.80 |
-1.06 |
-6.86 |
-0.06 |
|
HuetCristobal |
-8.23 |
-7.00 |
-1.23 |
-7.52 |
-0.52 |
|
LeclairePascal |
-9.77 |
-9.70 |
-0.07 |
-10.57 |
-0.87 |
|
ToskalaVesa |
-14.06 |
-13.80 |
-0.26 |
-14.09 |
-0.29 |
|
Average Difference |
|
|
-1.12 |
|
-0.51 |