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.

Methodology

Period

2000 Hatsu Basho～2026 Natsu Basho

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.