when is the optimal strategy is to throw a badminton match?

By Laura Albert McLay

I’ve been following the badminton scandal in the news. First, let me say that I never thought I’d hear the words “badminton” and “scandal” in the same sentence. I thought that this was one of those rare cheating events that sometimes happens. The evidence suggests that the optimal strategy may sometimes be to lose on purpose.
In previous Olympics, the entire set of badminton matches were in a tournament with knockout rounds. A team could apparently not chance their seed or path to gold. In this Olympics, there was a new preliminary pool round with the performance in the pool leading to seeds in the later single elimination tournament with 16 teams. This introduced a wrinkle to the optimal strategy. Now a team might want to think about how they could optimize their seed/path in the single elimination rounds. Obviously, introducing a path to the gold by doing something other than winning every possible match potentially invites trouble. However, the badminton rounds of play with a preliminary pool and later tournament is like what happens in volleyball, basketball, soccer, and other sports. I haven’t seen “lazy” players obviously throwing a match. Usually, winning more in the preliminary round only makes it easier later on.
Apparently, there is a huge incentive in badminton to throw matches. The badminton magazine Badzine conducted a study about throwing matches, since it is common knowledge that the Chinese throw matches. They found that matches were won by “walkovers” or early retirements in 20 of 99 (20%) of all-Chinese matches [link to article]. Walkovers/retirements occured in 5.3% of matches when non-Chinese athletes played their compatriots and in 0.74% of the matches between Chinese athletes and non-Chinese athletes. So the Chinese “throwing” rate is an outlier, which suggests that the Chinese badminton players are all in cahoots with each other. The Olympics scandal, however, included two Chinese teams, one Indonesian team, and one South Korea team.
Here is why the players’ strategy changed from winning all preliminary games to throwing a match:

The attempt to throw the two matches in the women’s doubles had it roots in a surprise result earlier in the day when the Chinese second seeds, Tian Qing and Zhao Yunlei, were beaten by a Danish pair. The result meant that Yang and Xiaoli had to lose to avoid meeting their compatriots before a potential showdown in the final.
A similar desire to avoid the hot favourites seemed to have cross-infected the second match, between  South Korean third seeds Ha Jung-Eun and Kim Min-Jung and Indonesian pair Meiliana Juahari and Greysia Polii [link]

And yes, the cheating was so obvious that people in the audience booed the athletes’ lack of effort:

Lori Halford, 35, who had paid £40 along with her husband for tickets to the evening session, told The Independent: “It was immediately clear that something wasn’t right. The first shot went into the net, then the next shot went into the net. The next return went under the net. There was no speed or strength to their play. There was a complete contrast to the others playing in different games who were giving it everything they could.” [link]

Throwing a badminton match is not dissimilar to sumo wrestlers throwing matches, which was discussed in detail in Freakonomics.