Reproducing MLB's Park Factors: NFL Stadium Factors

The MLB has park factors to normalize stats earned in parks such as Coors Field or Petco Park, parks with an abnormal bias towards pitching or hitting. (See Wikipedia entry for more info and explanations.)

We all know some NFL stadiums usually have higher scoring games than others, especially in the winter. If you owned Tom Brady or Randy Moss last year, you were burned when they put up stinkers in Week 15 , when the temperature was near freezing and winds were up to 25 miles per hour.

We know that Lambeau Field has one or two or three snow games each year, and we know that the Georgia Dome always has temperatures in the 70s.

Can we use this information to create "Stadium Factors" for the NFL? Using pro-football-reference.com’s indispensable schedule page (which lists points, passing yards, and rushing yards, the only site that has those stats on the schedule page itself), I did just that. I looked at 2005-2007, plus the five or six games played this year to create a factor for points score, passing yards, and rushing yards.

An easy way to think of the factors is, how many more times the amount of points/passing yards/rushing yards are scored/gained at home than on the road? A 1.18 factor means there are 1.18 times more scored/gained at home than on the road.

Let’s get to the data:

NFL Stadium Factors

Team	Stadium	Pts	PassYds	RushYds
ATL	Georgia Dome	1.247	1.110	1.049
STL	Edward Jones Dome	1.180	1.073	1.120
PIT	Heinz Field	1.132	1.007	1.110
KC	Arrowhead Stadium	1.108	1.041	0.963
HOU	Reliant Stadium	1.103	1.086	0.986
BUF	Ralph Wilson Stadium	1.076	0.996	1.040
CHI	Soldier Field	1.062	0.921	1.083
TB	Raymond James Stadium	1.056	0.917	1.024
TEN	LP Field	1.044	1.029	0.924
CIN	Paul Brown Stadium	1.033	0.996	1.037
DAL	Texas Stadium	1.026	1.041	0.978
MIA	Dolphin Stadium	1.009	1.036	1.000
BAL	M&T Bank Stadium	1.008	0.977	1.040
WAS	FedExField	1.007	0.954	0.966
OAK	Oakland-Alameda County Coliseum	1.007	1.041	0.905
MIN	H.H.H. Metrodome	1.003	1.104	1.008
SD	Qualcomm Stadium	1.000	0.985	0.987
NYG/NYJ	Giants Stadium/ Meadowlands	0.999	0.919	0.971
DET	Ford Field	0.989	1.084	0.935
DEN	Invesco Field (Mile High)	0.978	1.011	1.059
SEA	Qwest Field	0.963	0.937	1.076
CAR	Bank of America Stadium	0.961	0.965	1.042
CLE	Cleveland Browns Stadium	0.950	1.034	1.014
ARI	University of Phoenix Stadium	0.945	1.054	0.926
NO	Louisiana Superdome	0.913	0.942	0.988
SF	Candlestick Park	0.911	1.033	0.875
PHI	Lincoln Financial Field	0.901	1.029	0.959
IND	RCA Dome/ Lucas Oil Stadium	0.899	0.923	1.015
JAX	Jacksonville Municipal Stadium	0.898	1.019	0.963
NE	Gilette Stadium	0.876	0.954	1.014
GB	Lambeau Field	0.869	0.911	1.009

 

*I know Arizona’s new stadium opened in 2006, and that Indianapolis’ new stadium opened just this year. But I counted their stats back to 2005 anyway. And the 49ers’ stadium isn’t formally known as Candlestick Park, so if you prefer Monster Park or Bill Walsh Field, fine by me.

Obviously, the domes are at the top, and the cold-climate/bad-weather stadiums are near the bottom. Arrowhead Stadium, well-known for their massive home-field advantage, also come at the top.

If we apply the rushing and passing factors (passing factor to receiving yards; factors are applied by dividing stats by the factor itself) and keep touchdowns constant—I haven’t figured out how to change the points factor to touchdowns, and at the moment it seems like it’ll make it worse, because there might be a stadium where half of the home points were field goals, and another stadium where only a quarter were field goals; the touchdown-field goal rate won’t be the same in all stadiums, a problem to which I’m trying to come up with a solution—here’s how the top-10 changes:

Top-10 RBs

Before adjustments		After adjustments
Name	PPG	Name	PPG
Clinton Portis	17.8	Clinton Portis	18.2
Ronnie Brown	17.3	Frank Gore	18.1
Marion Barber	17.2	Marion Barber	17.2
Frank Gore	17.0	Ronnie Brown	17.2
Brian Westbrook	16.3	Brian Westbrook	16.4
Michael Turner	16.1	Matt Forte	15.8
Matt Forte	16.1	Michael Turner	15.7
Reggie Bush	15.0	Reggie Bush	15.4
Brandon Jacobs	14.1	Brandon Jacobs	14.4
Steve Slaton	13.7	Steve Slaton	13.7

 

Not much difference, except that Frank Gore shoots up with more than a point-per-game difference before and after.

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These factors will be updated weekly on my Web site, hopefully the same time I finish the Reals and Surreals.