Introduction

In this project, I am analyzing Japanese Sumo wrestling's tournament ranking table (番付, banzuke) to see what kind of wrestlers are at the top of the rankings.

Purpose of the project

I am analyzing this data because I have been asked about Sumo so much since I moved to the US (since I am from Japan), but I wasn't able to answer the questions very well. In fact, I have never watched a Sumo match in person. Through this project, I would like to learn more about Sumo wrestling, as well as be able to answer questions about the sport.

A little bit about Sumo

Sumo (相撲) is full-contact wrestling where two wrestlers (力士, rikishi) grapple and attempt to push or throw their opponent. The winner is the one who forces the opponent out of the ring or into touching the ground with any part of their body other than their feet. Generally, heavier wrestlers tend to be ranked higher since they are harder to move.

In Japan, Sumo is practiced professionally as a national sport. Japan usually holds The Sumo Grand Tournament six times a year, and each tournament has its own tournament ranking table.

There are about 700 wrestlers in total, and they are grouped into six divisions based on rank. The top 42 wrestlers are part of a group known as "幕内, makuuchi".

Sumo banzuke data set

A data scientist Mikhail Zhilkin put together a data set for official tournament ranking tables based on official information released by The Japan Sumo Association. I am using the data set for The 2019 Sumo Grand Tournament from data.world.

Data analysis

For this project, I am comparing the data for top 42 wrestlers over 20 years, quinquennially. I am analyzing January's tournament data for each year.

First, I am visualizing the top 42 wrestlers' weight and height, as well as their place of birth and ranking. I am also creating a second visualization that shows the number of wrestlers for each age and their countries of birth and ranks, over the years. These analyses were motivated by the following questions:

• Are Mongolian wrestlers really strong? I hear many strong wrestlers are from Mongolia, so I would like to know if this is true.
• The taller/heavier, the better? I would like to know if there is a correlation between the wrestler's height/weight and their rank.
• What's the best age for sumo wrestlers? As much as sumo is a physical sport, I know there are many wrestlers in their late 30s who are ranked high in Makuuchi division. I'd like to know the general tendency in terms of wrestler's age and rank.

I conducted the initial analysis using R. The original data sets are seperated by the years, and each has rankings for all six tournaments held in that year.

Therefore, for each year's data, I filtered the rows to only show January's top 42 wrestlers, and then combined the five seperated data sets. I also converted kilograms into pounds, centimeters into feet, and birth dates into ages (as of the time each tournament table was published).

The cleaned data has 210 rows and 12 columns. Each row represents a wrestler. The columns are as follows:

• basho: The year and month the tournament was held
• rank: The wrestler's rank (1 to 42)
• rikishi: The wrestler's name
• shusshin: The wrestler's country of birth
• country: The wrestler's country of birth (Japan, Mongolia, or elsewhere)
• weight_pounds: The wrestler's weight (lbt)
• height_feet: The wrestler's height (ft)
• height_feet_floor: The wrestler's height (ft) downwords to the nearest integer
• height_inches_reminder: The wrestler's height in inches subtracted by the value of heigh_feet_floor
• age: The wrestler's age (as of the time the tournament table was published)
• count: The wrestler's rank inside of the same age for the year

Visualization

Here, I'm creating two data visualizations. The first visualization shows 1) where the topmost wrestlers are from, and tires to find out 2) if taller/heavier wrestlers are higher-ranked, over two decades. The second one demonstrates how many wrestlers were at what age on the top 42 tournament table over time.

1. Relationships between height/weight and rank

For the first visualization, I created a scatter plot. Inside the scatter plot, each circle represents a wrestler in the Makuuchi (top 42) division. The x-axis shows the wrestler's weight in lbs, while the y-axis shows the wrestler's height in feet. The color shows the wrestler's rank (from 1 to 42). The circle(s) with yellow strokes represent wrestlers from Mongolia, in order to distinguish them easily since one of the questions I'm trying to answer is if Mongolian wrestlers are stronger in general.

By clicking the buttons from January 1999 to January 2019, you can select which year's data to show. The original chart shows data for January 1999.

There is also a filter feature that can apply to each year's visualization. By clicking the checkboxes, you can filter the wrestlers by whether they are from Japan, Mongolia, or other countries. At the same time, you can change the minumum and maximum ranks of the wrestlers shown. If you change the data's year, the filter feature will reset automatically and the scatter plot will have 42 circles to show.

In any of the state, you can see a wrestler's detailed information in a tooltip by hovering over a circle.

Findings from the visualization

The visualization demonstrates a few facts:

• Although there are occasional outliers, most of the Makuuchi wrestlers weigh around 280 ~ 400 pounds. Conversely, we can't see any strong tendencies of their height.
• It's not necessarily true that the taller/heavier the wrestlers are, the stronger. For example, in January 1999, Wakanohana (5'11", 289lbs) is ranked 2nd, whereas Akebono (6'8", 501lbs) and Musashimaru (6'3", 474lbs) are ranked 3rd and 4th respectively.
• More and more Mogolian wrestlers are coming into the Makuuchi division over the two decades. The numbers of Mongolian wrestlers increase from 1 (January 1999) → 4 → 9 → 10 → 6 (January 2019). The rumor -- that Mongolian wrestlers are generally strong -- appears to be only true in recent years. Still, most Makuuchi wrestlers are Japanese over all.

2. Makuuchi wrestler's age distribution

Next, I'm going to visualize how many wrestlers are at what age in the Makuuchi (top 42) division.

Similar to the first chart, each circle represents a wrestler, and the circle's color represents the wrestler's rank (1 to 42). Mongolian wrestlers are highlighted as yellow.

The x-axis shows the wrestler's age (when the tournament table was published), and the y-axis shows the number of wrestlers at each age. By selecting the button on top (from January 1999 to January 2019), you can select which year's data to show. Originally, the visualization represents the data for January 1999.

Findings from the visualization

The visualization demonstrates a few facts:

• Many high-ranked Makuuchi wrestlers are late 20s and early 30s. Younger and older wrestlers occasionally do well, such as Asashoryu (from January 2004, age: 23, rank: 1), and Kaio (from January 2009, age: 36, rank: 6).
• Kyokutenho (from January 2014, age: 39, rank: 39) was an unusually old wrestler to be registered in the Makuuchi division.
• You can find many wrestlers who stay in the Makuuchi division over the years such as Chiyotaikai (from January 2004, age: 27, rank: 3 / from January 2009, age: 32, rank: 4) and Hakuho (from January 2009, age: 23, rank: 1 / from January 2014, age: 28, rank: 2 / from January 2019, age: 33: rank: 2). Those wrestlers are the most successful ones who stay atop over many years throughout their career.

From these findings, it can be said that elements like wrestler's height/weight, place of birth, and age matter to a certain degree, but there seem to be many more factors that break the general tendency and determine their sumo-wrestling skills.