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Monday, January 26, 2004

Kauffman Park Effects

An email from Ron Hostetter inquired about the ballpark effect of Kauffman stadium because of a quote he saw in book on ballparks published in 1998. In essence the comment said: "The change from artificial turf to grass has changed baseball in this park. It is now a pitchers’ park. The number of hits, doubles and triples have been reduced significantly. Although the fences down the line and in the power alleys were brought in 10 feet in 1995, homering at the park remains more difficult than at a neutral park (about 15 percent more difficult). "

However, the last few seasons have seen the K act as a boon for hitters increasing run production by 30% for a ballpark factor of 130 as calculated in The Bill James Handbook 2004. I went back and pulled the numbers from baseball-reference.com and found the following;

	Home				Away			Index		

Games Royals Opp Opp%+ Games Royals Opp Opp%+ Royals Opp Overall
2003 80 433 512 18% 82 403 355 -12% 10% 48% 28%
2002 81 434 505 16% 81 303 386 27% 43% 31% 36%
2001 81 382 485 27% 81 347 373 7% 10% 30% 20%
2000 81 451 488 8% 81 428 442 3% 5% 10% 8%
1999 80 441 449 2% 81 415 472 14% 8% -4% 2%
1998 80 353 492 39% 81 461 407 -12% -22% 22% -1%
1997 80 387 434 12% 81 360 386 7% 9% 14% 11%
1996 80 372 369 -1% 81 374 417 11% 1% -10% -5%
1995 72 285 346 21% 72 344 345 0% -17% 0% -8%
1994 59 325 287 -12% 58 249 245 -2% 28% 15% 22%
1993 81 370 354 -4% 81 305 340 11% 21% 4% 12%
1992 81 314 346 10% 81 296 331 12% 6% 5% 5%
1991 81 344 378 10% 81 383 344 -10% -10% 10% -1%

91-94 302 1353 1365 1% 301 1233 1260 2% 9% 8% 9%
95-03 715 3538 4080 15% 721 3435 3583 4% 4% 15% 9%

Note: These stats include interleague games.

From the above chart it is interesting to note that in the 1991-1994 period (supposedly when the hitters had the advantage) the ballpark produced 9% more runs (a ballpark factor of 109) while from 1995-2003 when changes made it more amenable to pitchers it was also 109. For some reason the 1995 and 1996 numbers were much lower than in almost all the other years. One possible explanation is that weather patterns in Kansas City changed over the last few years producing hotter, sunnier, and breezier days than previously and so even though the changes in the 1994 offseason made the park more of a pitcher's park, the weather more than compensated in the last few years. Another possible explanation is that the data is too variable to say definitively how much of an advantage or disadvantage hitters have at the K. The standard deviation when all years are taken into consideration is .15 which seems pretty big to me.

Perhaps the bigger question is why in 7 of the last 9 years the Royals opponents have scored so many more runs proportionately at the K than the Royals have? The opponent's huge numbers at the K scoring 15% more run while the Royals score only 4% more have inflated the park factor. So why is it that the Royals seem to give up so many runs at home? Email me if you have any ideas.

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