02 May 2012

What Effect Moving the Fences at Camden Yards Would Have?

I have been wondering how fence distance affects home runs.  I thought I had read somewhere that a ten foot difference results in a 20% difference in home runs.  However, I can not find that article, so I decided to figure it out myself.  I used Hit Tracker and simply graphed a section of the wall at Camden Yards with ten foot sections marked off.

In this section 138 home runs were hit from 2009-2011.  In the graph above, if the fence was at line 1 (the bottom most line), then 138 home runs would be hit.  If the fence is set ten feet back at line 2, then 108 home runs would have been hit.  That is a reduction of 30 home runs that were hit in that 10 foot space along this section of the wall.

The following graph shows the relationship between moving the fence back and home runs:

You can then use this information to predict the effect of moving a fence.

The graph above is a bit confusing.  Somehow my tired brain could not figure out how to do it.  Anyway, the way the x-axis works is that you go out to the furthest distance the fence could stand with no home runs and move back in.  The stretch of wall I looked at had a distance of 340 to 395 and correlates to the 80 mark.  Knowing that, we then can produce the following table showing how distance affects home runs over the course of three seasons:
Beginning End Projected Home Runs Actual Home Runs Percetage
260 315 469
270 325 417
280 335 367
290 345 321
300 355 278
310 365 238
320 375 201
330 385 167
340 395 137 138 100
350 405 109 108 80
360 415 85 83 62
370 425 63 62 46
380 435 45 47 33
390 445 30 31 22
400 455 18 17 13
410 465 9 12 7
420 475 4 2 3
430 485 1


Northwood said...

Thanks for the analysis. I have wondered this same thing, but from a competitive standpoint - How many of those home runs where Os and how many visitors? Given that a home run hitting OF costs more than a fast one, would moving the fences out 10 feet and giving up the Os HR allow the Os to develop faster gap hitting OF to give home field advantage over the more costly Red Sox and Yankees OF sluggers (although Granderson would still kick our butts).

Also, fly ball pitchers are cheaper than ground ball pitchers. Getting a long fly out with men on base instead of a HR could have a more significant positive impact on Os ERA than visitors.

Anonymous said...

Statistician says...

From a purely statistical point of view, extrapolating outside the rgion of data can be a little risky. It's subject to huge swings in variability. Any prediction within the 0-90 foot range should be alright. However, beyond that range, things might change drastically. Instead of 167 projected HRs, there might be 180 or 190, depending on the number of guys out there with warning track power.

If there's any "long out" data out there (Data that has the number of 390 foot outs), this would give a better estimate of moving fences in.

To Northwood: It's a worthwhile thought. It worked in Memorial Stadium (See Ballpark Wanderer in Tom Boswell's "Why Time Begins on Opening Day"). Boswell mentions that O's pitchers lived by the maxim that fastballs on the outside corner would be long outs in the deep power alleys of Memorial Stadium.

Jon Shepherd said...

Of course, there are assumptions here that were used to extend our consideration of homeruns beyond the area for which we could test. I do not have a data set for long outs.