Analysis6
Is opening day really chaotic?
Conclusion
The most chaotic day is not opening day but the final day. Opening-day upsets were 35.8%, close to average, while Day 7 was the quietest at 32.8%. The rate rises to 37.8% on Day 13, 38.7% on Day 14, and 39.1% on the final day as pressure and fatigue accumulate.
How to read this number
An upset here means the rikishi who was clearly stronger on the pre-bout strength index lost. Day 1 sits at 35.8% and the final day at 39.1%. Three points sounds small, but across roughly two thousand bouts per day it is too large to dismiss as noise.
At least three forces push the late days upward: opponents are matched by record, the winning and losing thresholds converge, and fifteen days of wear accumulate. All three work in the same direction, making the closing days the least predictable.
As a viewing guide, the final days reward anyone hoping for a surprise, while the middle of the tournament is the most orderly, with Day 7 the quietest at 32.8%. Opening day certainly feels tense, but that tension does not show up in the results.
Methodology
- Period
- Hatsu 2000 through Natsu 2026
- Sample
- Makuuchi bouts with a strength-index gap of 40 or more before the bout
- Sample size
- Day 12,041 bouts, Final day 2,202 bouts
- Calculation
- Upsets by the higher-rated side divided by all qualifying bouts
- By day
- Day 135.8%, 7Day32.8%, 13Day37.8%, 14Day38.7%, Final day39.1%
How to read this
The strength index is updated only with results before each bout. Playoff bouts are excluded.