Sumo Debuts - Analysis of Trends Over Time
And Interesting Stories and Wrestlers Too
The big story of Sumo in the first half of 2024 is Onosato and Takerufuji. In the 3 complete tournaments, they won 2 of the Yusho and Onosato also had a Jun-Yusho. Something I noticed through my research on Yokozuna and Ozeki is that a key milestone is how young a Rikishi debuts in the Makuuchi. Wrestlers that go on to become Yokozuna debut younger, and it’s correlated to potential. Wajima was the oldest debuting at just 23 when he reached the Makuuchi. Onosato debuted at 23.5 years old. But what’s different is that Onosato and Takerufuji both went to college and had very successful careers, and with their experience could quickly work their way to the top division. Onosato’s college accomplishments let him debut at Makushita 10. Takerufuji simply dominated his way from Jonokuchi to Makuuchi.
This article is about looking at how young wrestlers debuted in Sumo in general. My criteria was simply age when they first appeared in any division above Maezumo, so the traditional 6. The trends in what age wrestlers debut at are really interesting and I think Onosato and Takerufuji in that sense are emblematic of the current era.
I used every Rikishi that participated in a Basho from January 1958 to the end of 2023 at the Jonokuchi level or above and had a birthday available. I then calculated age at debut in any of those 6 divisions.
Grouping by decades I think was pretty informative. Maybe in the future I’ll try to look at in a different way, but it does feel accurate just from my perspective as someone who looks at a lot of Sumo related data. Check it out!
I’ll walk through all of the columns and any trends that stick out.
First off for count, it’s just the number of wrestlers from 1958-2023 who I could find the birthday for. The first thing I noticed and then wondered about: could the 2020’s see a rebound rom the 2 decade downward trend in new debuts? That would be exciting. However, using the pace from the first 4 years of this decade that would put us at 615 debuts. I’m biased but what if they loosened up the restrictions on foreign Rikishi? That could potentially help get the recruit numbers up.
The mean is just the average, so average age at debut. The obvious trend is that since the 80’s, the age has been trending upwards and Rikishi are now debuting at 18+ on average. With 246 wrestlers, Onosato and Takerufuji can only drag up the average age so much, but as I said, I do think they represent a trend.
Median is just the entire population of wrestlers sorted by youngest to oldest and the median is the exact middle. I do find it interesting that the median wrestler was under 17 till the it hit 18.1 in the 2010’s. To me that shows an additional data point that wrestlers are much more likely to join at 18 now.
Standard deviation is just how you can expect ages to vary from the average age. So it means that there is more volatility in age. Looking at the data, my working theory is that the higher standard deviations in recent decades is more wrestlers going to college first. 22 year old college graduates will push the standard deviation up. I need to do research into that in the future, but at least for now, it’s the best theory I have.
Skew just represents which was the distribution leans. In other words, if the skews were negative, it would mean more wrestlers are below the average debut age. However, the positive skew here means that in all decades, more wrestlers have been older than the debut age than have been younger than it. The fact the skew has been getting less positive of late does potentially undermine1 my theory on there being more college wrestlers, but again that’ll require further research. I included skew because learning about skew is helpful and I also thought it’d be another interesting lens to look at ages through.
The min is the minimum age aka the youngest. For one, I did some light research and I couldn’t confirm it but it appears sometime in the 90’s they set a minimum age of 15 to be in Jonokuchi and above. The latest I could find was Kotoobata Keisuke in March 1993 Haru Basho when he debuted a little under a month before his 15th birthday.
Max is a similar story where they set the max age to debut at 25 sometime after Tomonohana Shinya debuted at nearly 28 years old! Eagle eyed readers might have spotted a 25.3 age debut in the 2020’s but I confirmed Kogomaru made his Maezumo debut in the Haru Basho of 2020 which started on his 25th birthday. A bit of a quirk of the way I did the data, but he did get in just under the wire.
Finally, I would like to note that as I only took wrestlers from the 50’s that participated in 1958 or later, that decade isn’t apples to apples with the other decades. Still, the fact that from 1950-1957 there were 3, 4, or 5 Bashos rather than our current 6 annual model means that there’s probably no perfect comparison between that decade and our modern Sumo.
So that was our look at age at Sumo debut. I think this data shows some pretty clear shifting of the trends. Furthermore, we learned about some age limits on both the low end (15) and the high end (25). I’ll eventually look into the amount of wrestlers with college background but for now we can see that Onosato and Takerufuji look representative of a broader trend, and going forwards I won’t be surprised if we see more top prospects who went to college rather than joining Sumo at 18 (or younger). Thanks for reading!
But not necessarily! I think it’s possible there’s a world in which skew gets less positive while there are still more college wrestlers. The lesser positive skew could potentially just be