Here’s something I hope you know: there are 30 MLB teams, which means that there are 30 distinct MLB ballparks (excepting the Sacramento Athletics, while they wait for their new Las Vegas stadium to be built).
Each ballpark has its own idiosyncrasies and quirks, which is part of the reason why games are so fun to watch. A hard-hit ball to left field at Fenway slams into the Green Monster and the batter is held to a single, while at Dodger Stadium, that same batter is trotting around the bases celebrating a home run.
Besides the obvious difference in park dimensions, weather and climate play a major role in affecting outcomes of baseball games. The weather is obviously going to be colder when games are played in places like New York and Chicago early in the season, while the thinner air at Coors Field means fly balls have a greater chance of ending up as home runs.
Per Fangraphs, Coors Field has the highest five-year Park Factor overall and one of the highest home run Park Factors in the game. Typically, a Park Factor score of 100 is league average, so every Park Factor score over 100 means that event occurs at that specific stadium more frequently.
For example, if the league average Park Factor for home runs is 100 and Rate Stadium, home of the White Sox, has a Park Factor home run score of 106, then home runs occur more often than they do at a league average park for home runs.
Fangraphs has a great explainer on Park Factors here for further reading, and they also calculate the Park Factors for each type of hit and batted ball and batter handedness. You can get pretty deep in the weeds with Park Factors!
Actually, let’s wade into some of those weeds right now.
White Sox Stadiums & Run Scoring
The Chicago White Sox have played at their current stadium, Rate Field, since 1991. Their previous ballpark, Comiskey Park, was actually located right next to the current stadium but demolished to make way for a parking lot and the new stadium’s concourse. The original home plate is actually still in the ground. One of my favourite memories of going to White Sox games as a kid was finding the home plate and taking a couple of practice cuts before going into the new stadium.
One of the ways you can analyse the effect of ballparks on baseball is by looking at the number of runs scored by both the White Sox and visiting teams. What I’m interested in is what kind of run scoring differences there have been between the two stadiums the White Sox have played in over the last several decades.
Now, I’m not doing any sort of normalising to take into account the different playing styles of baseball or the “steroid era” over the years. This is simply examining runs scored in the aggregate between the two stadiums, but we may very well see differences in scoring depending on the period.
Let’s first look at run-scoring comparisons between Comiskey Park, Rate Field and all other ballparks between the 1981 and 2001 seasons. The chart below shows the average amount of runs scored per game at games played at Comiskey Park and all other stadiums (1981 – 1991) and games played at Rate Field (1991-2001). There were only four seasons where the average runs per game at Comiskey were higher than all other stadiums in the game. In the next decade, there were only two seasons where the average runs per game at Rate Field exceeded the average at all other stadiums.
There could be a couple of different reasons. One is that the White Sox were just not that consistently good during these two decades. For the 20 seasons analysed, the Sox only won more than 90 games four times. Now, some of the seasons were strike-shortened, so that potentially pulls down the average runs per game. But the Sox’s total winning percentage for this time period is .513. They were almost perfectly average and I would expect an average team to score an average amount of runs per game.
Another factor could be dimension differences between Comiskey Park and Rate Field. Comiskey’s left- and right-field fences down the line were 362 feet from home plate and 420 feet to dead centrefield. When Rate Field was built, the park shrunk. Now the left- and right-field foul poles are 330 and 335 feet from the plate, respectively, and 400 feet to centrefield.
A smaller field likely led to more home runs and more runs. However, the fact that Rate Field consistently averaged fewer runs than other stadiums from 1991-2001 suggests to me that the park is not as hitter-friendly as other ballparks in MLB during that time.
Using the same type of Retrosheet data, I analysed all 30 MLB team’s run-scoring averages by month and year from 2014-2024 and put the findings into a dashboard you can access here.
The dashboard displays similar charts to the White Sox average runs scored above, with one chart showing 10-year aggregated averages and the bottom charts broken up by year and month.
A specific chart of interest for readers may be for the Seattle Mariners. Inspired by a recent episode of Effectively Wild, I looked at the park factors for T-Mobile Park and over the last three years, T-Mobile has been the absolute worst park in baseball for hitters. The only “good” part about T-Mobile’s park factors applies to pitchers – hitters strike out much more at T-Mobile Park than any other stadium.
There are tons of ways to examine park factors and apply them to players. For instance, not to pick on Andrew Vaughn some more [Editor’s note: Check out Jack’s previous article about Andrew Vaughn], but if he had been a Cincinnati Red for the last four seasons, he may have had 21 more career home runs playing at Great American Ball Park than playing at Rate Field.
Park factors show just how unique baseball is. While the rules apply to every game played throughout the whole season, the stadium variations throw in some gnarly curveballs for players to contend with.
Article by Jack Turek. Watch out for more Chicago White Sox content from Jack during the 2025 season. If you want to share your opinions with Bat Flips & Nerds audience of 10,000, then hit the “Write for us” link.
