Pythagorean expectation
The record that runs scored and allowed point to (the expected record), compared with the actual record.
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Pacific League
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| Team | Actual | RS/RA | Pythagorean pct |
Expected W-L | Actual vs expected |
|---|---|---|---|---|---|
| SoftBank | 91 - 49 (3) | 707 / 452 | .694 | 97.2 - 42.9 | −6.1 |
| Seibu | 79 - 60 (4) | 503 / 464 | .537 | 74.6 - 64.4 | +4.4 |
| Nippon-Ham | 78 - 62 (3) | 591 / 529 | .550 | 77.1 - 62.9 | +0.9 |
| ORIX | 65 - 76 (2) | 483 / 605 | .398 | 56.2 - 84.8 | +8.8 |
| Lotte | 63 - 77 (3) | 492 / 586 | .421 | 58.9 - 81.1 | +4.1 |
| Rakuten | 58 - 84 (1) | 473 / 555 | .427 | 60.7 - 81.3 | −2.7 |
The estimated figures are worked out by this site and are not official announcements.
What the Pythagorean expectation is
The Pythagorean expectation is an idea devised by Bill James, the father of sabermetrics, for reading a team's underlying strength from its runs scored and runs allowed.
The expected records on this page are the records that runs scored and allowed point to.
Reading the gap: it is not all luck
Overperforming the expectation reflects an ability to win close games - bullpen quality, late-game management - as well as the bounce of one-run games. Underperformance often comes from a mix of blowout wins and narrow losses. Not all of the gap is luck, but extreme gaps are known to move back toward the expectation in following seasons.
The list at the bottom of the page (covering the last 20 seasons) gives a sense of scale: gaps around plus or minus ten wins are among the largest on record there.
Frequently asked questions
What is the Pythagorean winning percentage?
An empirical formula devised by Bill James that gives the expected winning percentage from runs scored and allowed.
Why do actual records differ from expected records?
Because the same run totals can be distributed differently - winning the close ones versus piling up blowouts. Bullpen quality, late-game management and one-run-game fortune all show up in the gap, and extreme gaps tend to regress the following season.