Just before the Judo Grand Prix in Tel Aviv, Professor of Sports 
Economics Alex Krumer tells interesting and surprising research [translated from Walla 16/01/20]
The movie and book Moneyball has heightened awareness of the importance of data analysis in professional sports. Thus, delayed by a few decades, the sports industry has joined traditional industries like the capital market, which we could not imagine without in-depth analytics.
What is interesting is that in recent years, there has been a growing interest in sports competitions also from a very unexpected direction - the world of academia in general and economics and business administration in particular. This interest is based on a very simple thing - data quality and availability. Like Newton, who used apples to discover physics, scientists use sports competitions as a lab to study human functionality in a real competitive environment with very high incentives and pressures. Nowadays you can find data on almost every sports competition in the world and all that's left to do is ask the right research questions.
The Impact of Psychological Momentum
Although I have never engaged in judoka, as an economist, I have noticed the uniqueness of the competition structure that allows for the study of momentum. The problem is that there are two types of momentum. The first is strategic momentum, whereby a lagged competitor reduces efforts and thus increases the probability of a competitor taking the lead in the competition. The second type is psychological momentum that has same results, but with a psychological and non-strategic mechanism. It is very hard distinguish between them.
So what does this have to do with Judo? Well, judo competitions provide a perfect laboratory that allows us to identify and measure psychological momentum. In competing for the bronze medal, a contestant who loses in the semifinals still must compete with the judoka who won the consolation stage (repechage stage), a competition where competitors have no incentive! All that remains is to collect data on as many judo fights as possible (including judoka rankings, past fight histories, home advantage, etc.) and see if a contender after the consolation stage victory is more likely to beat the competitor who comes after the semifinal loss.
In a study I published [Psychological Momentum and Gender] with Professor Danny Cohen-Zada of Ben-Gurion University of the Negev and Dr. Ze'ev Stodiner of Ariel University in the Journal of Economic Behavior and Organization, we found that in men's competitions, the judoka with a positive psychological momentum (the one who won in the previous consolation phase) has about twice as much a chance to beat the semi-final loser. However, we found no evidence of psychological momentum in women's battles. The possible explanation for this gender difference may lie in gender differences in the effect of testosterone. Testosterone is known to improve performance in both men and women. However, in men only, success leads to an increase in testosterone levels in the blood, and failure results in its decline. In women, however, there is no significant relationship between previous performance and blood testosterone levels.
Now you ask: what is the connection between judo and the economy? Well, if you look at Wall Street during the financial crisis, you'll find that about 90% were men. If, like Judo, previous success influences decision-making and increases the desire to compete with excess risks (one of the side-effects of excess testosterone), then the path to a financial bubble formation is short. Therefore, adding women to the capital market may lower risk levels.
In another study I published [On Winning Probabilities, Weight Categories and Home Advantage in Professional Judo], in the Journal of Sports Economics, I researched whether there were more competitively balanced weights. Simply put, I examined whether one underdog was more likely to win a single fight than the underdog with a different weight. In Judo, you can choose two weights for each gender in which two judokans per country compete in the world championship. In the other five weights, only one contestant (from each country) may participate. So, should you prefer the latter whose world rank is higher? There is no clear answer. Apparently, in the up-to-66kg category in men's competitions, the underdog's chances of beating the favorite are significantly higher than the other weight categories.
Judo home advantage also plays a part.
In conclusion, the fact that Israel has earned the right to host The International Judo Grand Prix [Jan. 21, 2020) is of great importance in gaining Olympic ranking, because every victory is important. The thing is that, like soccer, Judo also has a considerable home advantage. For example, the odds of a 22-point win against an 8-ranked up-to 66-kg are only 30% in a contest where no Judako has any home advantage. But, if the underdog (ranked 22) competes in front of the home crowd, the entire gap is reduced and the two judokans have the same odds forever. Let's hope that the homelands will work in our favor in the upcoming competition in Tel Aviv.
Alex Krumer is a full-time professor of sports economics at the Department of Sports Management at the University of Molde, Norway, and lecturer in Sports Business Management in the Guilford Glazer Faculty of the Ben-Gurion University of the Negev. His research interests include sports economics, sports analytics, behavioral economics of competitions and decision making.
