Chapter 1: Incentives

“What do schoolteachers and sumo wrestlers have in common?”
Answer: both have incentives to cheat, and some do.

With the advent of performance-based testing, teachers started being graded based on their students’ scores. That led to incidents where teachers cheated on behalf of their students – in most cases without their knowledge.

By looking at artificially high scores in one year, along with blocks of same, strangely coincidental answers, the Chicago Public School system was able to identify cheating teachers. In 2003, they fired the 12 teachers with the most convincing evidence against them. The next year, the amount of suspicious activity decreased by more than 30 percent.

Sumo wrestlers also have strong incentives to cheat. As the book explains, there are six tournaments a year, with each wrester appearing in 15 bouts. If they have an 8-7 record (or better), they advance in the rankings. If they have a 7-8 (or worse), they drop.

Just by considering the odds, one would expect matches between an 8-6 wrestler and a 7-7 wrestler to be roughtly even, or slightly in the the 8-6 one’s favor. Yet the results differ substantially – in over 80 percent of these kinds of matches, the 7-7 wrestler wins.

One might say that the 7-7 wrestler has the incentive to try harder, and so he tries harder. That may be true, but by looking at the next meeting between the same two wrestlers, the winning percentages are very different. In the next meeting, the former 8-6 guy wins over 60 percent of the time. This kind of variance suggests strongly that some people don’t always try to win.

In 1996, two wrestlers were about to meet with the press with a tell-all story about the world of sumo, and they were going to name names. Strangely, before they could do the press conference, they died in the same hospital, hours apart from each other, and from the same respiratory ailment. Police never did an investigation, declaring that in spite of the concidence there had been no foul play. Hm.

Source: Sheryl WuDunn, “Sumo Wrestlers (They’re BIG) Facing a Hard Fall,” New York Times, June 28, 1996; and Anthony Spaeth, “Sumo Quake: Japan’s Revered Sport is Marred by charges of tax evasion, match fixing, ties to organized crime, and two mysterious deaths,” reported by Irene M. Kunii and Hiroki Tashiro, Time (International Edition), September 30, 1996.