Where Park Factors Fail: Case Study of an Extreme Park Effect

Where Park Factors FailCASE STUDY OF AN EXTREME PARK EFFECT

SABERSEMINAR 2015 @BLABABOUTBALL

How do parks really affect outcomes?

Park factors are great!◦ Calculated as averages, and should be applied to averages◦ E.g. when calculating wRC+ you adjust baseline up or down based on home park, not the player

But what happens at the extremes?◦ Do parks really affect all players equally? Probably not.

Difficult to analyze◦ Measuring a park effect requires large samples◦ Most parks are fairly neutral◦ Extreme parks tend to get altered


If only there were an old park with an extreme effect…


(Mostly) unchanged since 1940

At least one extreme park effect◦ 30%+ impact on doubles, >25% for both LHH and RHH

Fenway fits the bill on both fronts


Found a park… how do we examine it?

Split hitters into extreme groups and see if they’re affected differently

To do that:◦ Calculate 2B/PA deltas for visitors to Fenway vs. other road games, 1956-2014◦ Group hitters into quartiles each year by projected 2B/PA rate (using Marcel)◦ Find weighted averages by quartile and hand

And the results say…


For RHH, Fenway doesn’t discriminate

1st Quartile 2nd Quartile 3rd Quartile 4th Quartile0

0.01

0.02

0.03

0.04

0.05

0.06

∆=0.008 ∆=0.004 ∆=0.009∆=0.008

Actual RHH 2B/PA rates, by projected rate quartilesEx-Fenway 2B/PA rate Fenway 2B/PA delta


What about for LHH?

1st Quartile 2nd Quartile 3rd Quartile 4th Quartile

-0.00999999999999999

1.04083408558608E-17

0.01

0.02

0.03

0.04

0.05

0.06

∆=0.007 ∆=0.008∆=0.009

∆=0.015

1.19x 1.20x 1.21x

1.34x

Actual LHH 2B/PA rates, by projected rate quartilesEx-Fenway 2B/PA rate Fenway 2B/PA delta


Do Fenway’s changes matter? Yes…

1960

1961

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90

100

110

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130

140

150

160

Average 2B/PA Fenway Park Effect, by Batter HandL (5 yr avg) R (5 yr avg)

CF flagpole

CF board

Roof suites

EMC Club

Monster Seats

Aux. press boxes

Budweiser RF Roof

Coca Cola Party Deck


… But not for RHH/LHH weirdness

1960

1961

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-0.010

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

Q4 Delta - Q1 Delta, by Batter HandL (10 yr avg) R (10 yr avg)

CF flagpole

CF board

Roof suites

EMC Club

Monster Seats

Aux. press boxes

Budweiser RF Roof

Coca Cola Party Deck


So what is the explanation?It’s all about asymmetry:

Data source: Gameday 2007 hit data, converted to feet using method from Peter Jensen: http://www.hardballtimes.com/using-gameday-to-build-a-fielding-metric-part-1/

75th percentiledistance, by

batter quartile

25th percentiledistance, by

batter quartile

http://www.hardballtimes.com/using-gameday-to-build-a-fielding-metric-part-1/

http://www.hardballtimes.com/using-gameday-to-build-a-fielding-metric-part-1/

pbandj

Simplify the explanation: Fenway's dimensions are following the shape of these curves for LHH, so shifting batted ball distribution outward can have a disproportionate effect on outcomes, which is exactly what you see in the results.

pbandj

In contrast, for righties the shape of the park is intersecting these curves more arbitrarily, in such a way that small changes DON'T have a big impact on outcomes - all RHH benefit/suffer from the larger dimensions in RF and the wall in LF in about the same way.


Conclusions Shocking revelation! Some lefties can exploit Fenway’s dimensions more than others.

More interesting: at the extremes, park effects can impact different types of players differently

But… there may not be another park effect like this one, now or ever


Questions?


Appendix: Pitchers are not the difference

Avg 2B/PA allowed vs. batter hand Avg wOBA allowed vs. batter hand

Batter group P faced ex-Fenway P faced at Fenway P faced ex-Fenway P faced at Fenway

LHH 4th quartile 0.042 0.046 0.334 0.331

LHH 1st quartile 0.041 0.046 0.335 0.332

Difference 0.001 0.001 -0.001 -0.001

Batter group P faced ex-Fenway P faced at Fenway P faced ex-Fenway P faced at Fenway

RHH 4th quartile 0.041 0.043 0.323 0.329

RHH 1st quartile 0.041 0.043 0.324 0.330

Difference -0.001 0.001 -0.001 -0.001

Date post:	17-Jan-2017
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Where Park Factors Fail: Case Study of an Extreme Park Effect

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