Where Did the Parity in Baseball Go?
League-wide parity was once a defining feature of Major League Baseball. This season has been a different story.
In baseball, the best hitters fail nearly 70% of the time—and the worst only about 10% more often. A team that wins six out of every ten games is a World Series contender, while one that wins just four in ten is likely near the bottom of the standings. In other words, the margin for error in baseball has traditionally been razor thin. To the naked eye, the league’s best and worst teams can appear almost indistinguishable.
This runs contrary to other sports, such as Football, where it is not uncommon for teams to flirt with a perfect season while others struggle muster but one victory. This exists at lower levels of the game as well. This year’s top seed in the College World Series—Vanderbilt—failed to win just 16 of its 58 games. Meanwhile, the College Football Playoff featured an undefeated Oregon squad alongside three other teams (Notre Dame, Indiana, and Boise State) with just one loss each.
However, we are now tracking towards the (arguably) worst team in modern baseball history, the 2024 Chicago White Sox, having to relinquish that infamous title after just one year to the 2025 Colorado Rockies. On the other hand, as of today (May 29th), we are on pace to have four 100+ win teams and to break the record for most 98+ win teams (six), set just three years ago in 2022.1 This season has also seen a number of lopsided games, with five decided by a margin of 15 or more runs—two of them by over 20.2
Is league parity in baseball dying?
An Imbalance of Power
Baseball Reference has a fairly intuitive rating system, aptly named “Simple Rating System” (SRS). At its core, SRS estimates how a team would perform against a league-average opponent on a neutral field and environment. An SRS of 1.0 means a team would be expected to beat an average team by one run in a neutral setting, while an SRS of 0.0 defines an exactly average team.3
So far in the 2025 season, we are seeing the largest standard deviation in team SRS since at least the league’s expansion to 24 teams in 1969. This high variability indicates the widest dispersion of team quality in over five decades. A smaller standard deviation would suggest teams to be more closely clustered around the league average, but this year’s larger spread suggests a league with greater disparities—more dominant teams at the top, and more really bad teams at the bottom.
If we assume a normal distribution, approximately 68% of the data should fall within one standard deviation of the mean. Under that assumption, 2025 is on track to give us the first year in which less than 68% of teams are within +/- 1 run of the league average. While the trend hasn't been a perfectly linear rise, there has been a gradual and noticeable increase in SRS standard deviation of the past 30 to 35 years.
Showing in the Standings
The standard deviation in wins (per 162 games) is also at its highest point since the ‘69 expansion. We are currently on track for a league-wide standard deviation of 17.3 wins over the full 162-game season—nearly two full wins higher than any other season on record. It should also be noted that six of the eight highest standard deviations in wins have come in the past eight seasons.
It is not just an outlier at the top or bottom skewing the numbers. When comparing the average run differential of the top five and bottom five teams, 2025 shows the widest gap on record—continuing a broader trend of a widening gap of late.
Even after removing the historically awful Colorado Rockies from the equation, the findings still hold. We’re still left with an all-time high SRS standard deviation of 0.92, a wins/162-game standard deviation of 14.3 (eighth-highest), a run differential standard deviation tied for the highest on record at 1.0, and a still record-setting average run differential gap of 3.0 between the top five and bottom five teams.
The Impact of Payroll Disparities
It would be natural to see this growing disparity and immediately point a finger at the mega-contracts and big-spending franchises that have dominated headlines in recent years as the root cause. To all fans of the small-market low-payroll teams, I extend my sincere apologies, but the evidence just doesn’t strongly support that theory. I’ll be writing more extensively in the near future about the correlation (or lack thereof) between team success and payroll, so I won’t dive too deep here and spoil what’s to come.
For now though, in 2025 the correlation coefficient between team payroll and SRS is 0.551, and 0.562 between payroll and wins. That suggests roughly 30–31% of the variation in performance can be explained by payroll—decent, but far from overwhelming evidence. Further, 2025 ranks just sixth and fifth in SRS–payroll and win–payroll correlation, respectively, since the 1995 season. By comparison, the 2019 season—which had the second-highest standard deviations in both SRS and run differential—ranks fifth and ninth in those same metrics. The season with the strongest correlation between payroll and performance, 2016, landed near the middle of the pack in both SRS and run differential disparity. Spending matters—but there’s clearly much more at play.
It’s hard not to notice the creeping trend of declining parity in Major League Baseball. I’m not suggesting this is necessarily bad for the game. After all, college football has seen massive success with enormous performance gaps between the top and bottom teams. The same goes for the NBA, which this year featured two squads with winning percentages over .750, and three who couldn’t surpass the .250 mark.
I don’t think the focus of this should be around whether or not this is inherently good or bad for the game, but rather what kind of league environment we’re heading toward. Whether the future favors a return to power-balance or continues down a path of growing disparity, the game will endure—and so will our love for Americas favorite pastime.
Top on-pace win totals are the Tigers (105), Phillies (104), Yankees (103), Cubs (101), Dodgers (98) and Mets (98).
Cincinnati Reds (24) vs. Baltimore Orioles (2) on April 20th and the San Diego Padres (21) vs. Colorado Rockies (0) on May 10th.
Standings won't reveal all at midpoint of season, by Will Leach