The domination of one-run victories in Major League Baseball

Every day I review the prior day/night’s 15 MLB games results when all 30 MLB teams play and that’s most days. I often notice that there are a fair number of final scores in which the game was decided by one run. I wondered, are one-run game outcomes more prevalent versus all MLB game outcomes? It sure seems that way.

Almost Cooperstown is a reader-supported publication. To receive new posts and support my work, consider becoming a free or even a paid subscriber.

Here’s what I found:

Roughly 28% to 30% of all modern MLB regular-season games are decided by one run.

The number usually lands around 29% and generally ranges from 27% — 31%.

In many recent seasons, MLB has finished with approximately 700–730 one-run games out of 2,430 total games. This works out to just under 3 out of every 10 games.

Historically, one-run games were even more common in lower-scoring eras such as the 1960s as well as the so-called “Dead Ball Era,” while high-offense periods tend to reduce the percentage slightly.

In some seasons teams can outperform the average by winning an overweighted number of one-run contests. Generally, it is thought that for those teams, at some point they will regress toward the mean. But sometimes it can last an entire season! Remember the 2023 Miami Marlins? Those Marlins set the all-time AL/NL record for consecutive wins in one-run games by starting the 2023 season 12–0 in such contests. They ultimately finished the 2023 season with an incredible 33–14 record in games decided by a single run. It did not help them in their Wild-Card series loss to the Philadelphia Phillies.

Dominant teams (like the Dodgers), more often win by larger margins and don’t total as many one-run victories.

I wondered if the numbers hold up in the postseason? Or are there more or fewer one-run games in the playoffs? It turns out that roughly 32%-38% of postseason wins are by one run. The better the bullpen the higher that number can go sometimes exceeding 40%.

I found that a typical distribution of MLB game margins looks like this:

Margin of Victory

Approx. % of Games

1 run ~28–30%

2 runs ~16–18%

3 runs ~13–15%

4 runs ~10–11%

5+ runs — 26–40% overall progressively smaller individually

So even though blowouts collectively add up to a large share of games, one run games are far and away winners compared to any other outcome. What I thought I was seeing — is what was happening.

Here’s what I came up with as a graphic from data ending 2023

There are reasons for this:

• Overall, MLB scoring is relatively low compared with sports like basketball and football (hockey may even have more one-run contests?)
• Bullpens compress scoring late in games
• Home teams stop batting after taking the lead in the 9th inning, naturally preserving one-run margins
• Managers aggressively optimize late innings in close games keeping games closer.

But when it comes to playoff teams, they don’t necessarily play more one-run games overall. Instead, they tend to win a higher percentage of the one-run games they play, and/or convert close games into wins more efficiently than average teams. And that’s a reason they are playoff teams. A .500-ish team might go 24–28 in one-run games while a playoff team might go 33–22. An elite postseason team (think Dodgers), may dominate blowouts and still survive close games

Regression to the mean is always on the horizon

Sabermetric research shows that extreme success in one-run games often regresses the next season. Teams can skillfully win close games, but records in one-run games such as 40–18 or 35–15 are not thought of as being sustainable.

Indications and reasons

Teams with mediocre run differential but outstanding one-run records often overperform their true talent level. Teams with strong run differential but mediocre one-run records are often thought of as “better than their record”.

There’s also an interesting structural baseball quirk:

A two-run lead behaves very differently from a one-run lead because a solo HR can tie a one-run game but cannot erase a two-run deficit.

That makes managers treat one-run situations with maximum urgency, which paradoxically helps preserve them.

Historically, Dead Ball Era baseball produced huge numbers of one-run games in part because there were fewer teams. The high-offense steroid era reduced the percentage somewhat and today’s current bullpen usage and specialization has pushed one-run frequency back up.

The most popular score for an MLB game

Did you wonder? I did. A final score of 3–2 has historically been one of the most common exact MLB scores, which helps reinforce the dominance of one-run outcomes.

Thanks for reading Almost Cooperstown! This post is public so feel free to share it.

Has MLB ever had all 30 teams play one-run games on the same day?

I thought that might have happened, but the answer is no. When MLB had eight teams or even ‘only’ 16 teams as it did for many years, the chances were greater as there were as few as four or eight games played. With 15 games on a full schedule day that’s why it’s never happened. At least not yet.

Mathematically, since about 29% of MLB games are one-run games, then the odds of 10 straight games all being one-run games are roughly about 1 in 250,000. 15 games all ending by one run: about 1 in 100 million+

Real baseball outcomes are not perfectly independent, but the point remains having a full league-wide one-run day would be an astonishing statistical anomaly. You can bet I will be paying attention if it does!

About the Author: Mark Kolier along with his son Gordon co-hosts a baseball podcast called ‘Almost Cooperstown’. He also has written baseball-related articles that can be accessed on Medium.com and Substack.com.