Last updated August 15, 1997
In Rob Neyer’s July 21, 1997 Chin Muzak he observes that both the Rockies and Burt Shotton’s Phillies had extreme Home/Road splits while playing in extreme hitters parks and asks “Can it be coincidental that they happen to play in perhaps the best hitter’s parks ever?” Rob also had followup columns discussing letters from Guy Tyler on August 8 and from Chris Aberson and John Rickert (me) on August 15. A further followup from Tim Ruane was printed August 19. Here’s a start at looking at the question.
Hitter’s Parks
I went through the latest edition of Total Baseball and listed teams with batters park factors of 105 or greater. (i.e. the park inflates offense by 4.5% or more) I then found all teams that maintained such a large park factor for five or more seasons. Since several teams dipped slightly below 105 for a season and came back, I expended the list to also include teams with 6 or more seasons with only one year of batters park factor below 105.
I then used the Baseball Encyclopedia to find the records at home and on the road for each team and compiled the results. A summary is in the table below:
| Team | Years | W-L | Pct. | Home | Road | Difference |
|---|---|---|---|---|---|---|
| Red Sox | 1989-94 | 462-463 | .499 | 258-211 .550 | 204-252 .447 | .103 |
| Braves | 1983-92 | 749-865 | .464 | 396-409 .492 | 353-456 .436 | .056 |
| Cubs | 1983-91 | 714-737 | .492 | 389-338 .535 | 325-399 .449 | .086 |
| Red Sox | 1964-84 | 1761-1574 | .528 | 953-715 .571 | 808-859 .485 | .086 |
| Cubs | 1976-80 | 379-431 | .468 | 214-192 .527 | 165-239 .408 | .119 |
| Cubs | 1967-73 | 592-533 | .526 | 322-241 .572 | 270-292 .480 | .092 |
| Reds | 1963-69 | 602-530 | .532 | 327-238 .579 | 275-292 .485 | .094 |
| Cardinals | 1959-65 | 587-522 | .529 | 328-227 .591 | 259-295 .468 | .123 |
| Dodgers | 1956-61 | 507-419 | .548 | 267-196 .577 | 240-223 .518 | .059 |
| Red Sox | 1946-59 | 1193-963 | .553 | 683-396 .633 | 510-567 .474 | .159 |
| Tigers | 1938-46 | 749-636 | .541 | 412-285 .591 | 337-351 .490 | .101 |
| Cardinals | 1938-42 | 450-314 | .589 | 241-145 .624 | 209-169 .553 | .071 |
| Phillies | 1929-37 | 562-814 | .408 | 320-359 .471 | 242-455 .347 | .124 |
| Phillies | 1918-26 | 503-826 | .378 | 266-391 .405 | 237-435 .353 | .052 |
| Browns | 1921-26 | 466-453 | .507 | 263-200 .568 | 203-253 .445 | .123 |
| Highlanders | 1903-07 | 395-338 | .539 | 213-153 .582 | 182-185 .496 | .086 |
| TOTAL | 10,671-10,418 | .506 | 5852-4696 .555 | 4819-5722 .457 | .098 |
The won-lost percentage for home teams for 1900-1995 was .542, so road teams W-L Pct. was .458 and the difference was .084.
The overall road Pct. for the teams was .457, very close to a normal road percentage. If we decide that this means that the teams were overall average teams, then their home winning percentage should be .541. Instead, it was .555. If we assume that the teams were average teams, then the probability of deviating that far from the expected number of wins at home is approximately 0.9%, indicating that there probably is a small advantage for teams playing in extreme hitters parks.
Of course, an alternative explanation is that the teams were really slightly better than average, as was indicated by their overall .506 W-L pct. If this assumption is used then the teams would come out better at home (but only at the 17% confidence level) and worse on the road (also at a 17% level), however the results are not statistically significant.
The likelihood of average teams deviating as far from .500 as .506(or farther) is roughly 25%. again, not an unreasonable occurance.
There were also eight teams that played in offensive parks for four consecutive years, or four out of five years. They produced the following results:
| Team | Years | W-L | Pct. | Home | Road | Difference |
|---|---|---|---|---|---|---|
| Rockies | 1993-96 | 280-305 | .479 | 163-128 .560 | 117-177 .398 | .162 |
| Braves | 1976-79 | 266-380 | .412 | 147-175 .457 | 119-205 .367 | .090 |
| Braves | 1970-73 | 304-335 | .476 | 161-159 .503 | 143-176 .448 | .055 |
| Reds | 1955-58 | 322-294 | .523 | 182-126 .591 | 140-168 .455 | .136 |
| Browns | 1932-35 | 250-359 | .411 | 130-171 .432 | 120-188 .390 | .042 |
| Red Sox | 1934-38 | 396-364 | .521 | 226-153 .596 | 170-211 .446 | .150 |
| Indians | 1916-19 | 322-252 | .561 | 169-114 .597 | 153-138 .526 | .071 |
| Reds | 1902-05 | 311-274 | .532 | 175-125 .583 | 136-149 .477 | .106 |
| TOTAL | 2451-2563 | .489 | 1353-1151 .540 | 1098-1412 .437 | .103 |
The `Best’ Hitter’s Parks
Here’s a list of the highest Batter Park Factors from Total Baseball:
- 129 Colorado NL 1995-6
- 116 Colorado NL 1993-4
- 115 Chicago NL 1971
- 113 Chicago NL 1969, Philadelphia NL 1933-4
- 112 Boston AL 1976-7, Chicago NL 1978, Atlanta NL 1977, Chicago NL 1970, Boston AL 1956, Philadelphia NL 1932 Philadelphia NL 1923-4, Boston NL 1900
- 111 Chicago NL 1985, Atlanta NL 1978, Chicago NL 1977, Boston AL 1978, Cincinnati NL 1967, Los Angeles AL 1961 Boston AL 1954, Chicago NL 1916, New York AL 1905 Cincinnati NL 1903,05
- 110 Boston AL 1966, St. Louis NL 1961-2, Brooklyn NL 1957 Boston AL 1950-1, Detroit AL 1940-1*, Philadelphia NL 1935-6 Cleveland AL 1918, Cincinnati NL 1902The won-lost records for these teams (data from Pete Palmer) were
BPF W-L Pct. Home Road Difference 129 160-146 .523 99-54 .647 61-92 .399 .248 116 120-159 .430 64-74 .464 56-85 .397 .067 115 83-79 .512 44-37 .543 39-42 .481 .062 113 208-255 .449 116-108 .518 92-147 .385 .133 112 737-823 .472 403-376 .517 334-447 .428 .090 111 843-876 .490 486-385 .558 357-491 .421 .137 110 927-895 .509 511-399 .562 416-496 .456 .105 TOTAL 3078-3233 .488 1723-1433 .546 1355-1800 .429 .116 Difference is calculated using more than 3 decimal places, so rounding error might occasionally make the Difference value appear incorrect.
The Rockies are clearly an outlier on this chart, but the trend is not entirely clear. The teams in the next best hitters parks, The Rockies in Mile High and the Cubs in Wrigley, had below average differences.
When we get to the BPFs with several teams, the numbers seem to be staying around a slightly larger than normal difference.
*I received a note from DaveB saying:
Recently I watched "The Life and Times of Hank Greenberg" and in the film, he talked about how in 1940 the main reason for the Tigers success (they won the Pennant) was the fact that they were stealing signs. They only did this at home as they had a guy in the upper deck bleachers of Briggs Stadium with binoculars giving them signals. Greenberg said that he and Rudy York were getting fat HR numbers during this time. I'm not sure for how many years this went on, but it is very interesting that one of the largest park factors in the history of baseball occurred at Briggs stadium from 1940-1941. I'm quite certain that the sign-stealing was the main contributor to the high home Batter Park Factor of that Tiger era.
Pitcher’s Parks
There were twelve teams that played in “pitcher’s parks”. (batters park factor of no more than 95 for either 5 or more consecutive years or for all but one of 6 consecutive years) Their overall won-lost percentage was .482. At home they were .531, on the road .434, a difference of .097.
Team Years W-L Pct. Home Road Difference A’s 1991-95 366-378 .492 198-173 .534 168-205 .450 .084 A’s 1978-87 723-844 .461 402-380 .514 321-464 .409 .105 Astros 1975-84 784-784 .500 449-333 .574 335-451 .426 .148 Padres 1971-82 799-1082 .425 438-506 .464 361-576 .385 .079 Angels 1971-76 446-518 .463 231-257 .476 215-264 .449 .027 Dodgers 1962-71 883-739 .544 465-347 .573 418-392 .516 .057 Astros 1962-66 333-475 .412 198-206 .491 135-269 .334 .157 Braves 1949-61 1100-903 .549 581-418 .582 519-485 .517 .065 Orioles 1954-58 330-437 .430 191-192 .499 139-245 .357 .142 Braves 1933-40 554-665 .454 305-297 .507 249-368 .404 .103 Yankees 1931-35 475-285 .625 258-120 .683 217-165 .568 .115 Senators 1906-10 279-477 .369 168-203 .453 111-274 .288 .165 TOTAL 7072-7587 .482 3884-3429 .531 3188-4158 .434 .097 Summary
Category W-L Pct. Difference Extreme Hitter 3078-3233 .488 .116 Long-Term Hitter 10,6711-10,418 .506 .098 Med.-Term Hitter 2451-2563 .489 .103 All .500 .084 Long-Term Pitcher 7072-7587 .482 .097 This is (thin) evidence that there is an effect and that it grows stronger in more extreme parks, but it’ll take some statistical tools to pull it out. What I suspect is that the Rockies extreme split is mostly a coincidence and that (much like the Twins a dozen years ago) their Home/Road splits will move closer to normal.
After all, what is “uniqueness”? Are the Metrodome, Kaufmann Stadium, Forbes Field and the Polo Grounds unique if their effect on runs scored is close to zero? If so, which is `uniquer’, a “neutral” Polo Grounds, a hitter’s Coors Field or a pitcher’s Astrodome?
Further study is needed to answer the question, but there might be an effect. If it exists it’s small – worth maybe one win a year. Not much, though the 1978 Red Sox and the 1967 Red Sox, might disagree
Further things to look at - Teams playing in pitchers parks for four consecutive seasons (there are three)
- Teams with `park factors’ of 100
- Teams in short-term `extreme’ pitcher’s parks
- There’s probably something else…
- e-mail me with useful comments, suggestions, corrections
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