The way it works right now, the reigning champion does nothing until a challenger has earned the right to face him by winning a candidates tournament. Then the winner of the candidates tournament faces the reigning champion in a match for the title. Carlsen, as I understand it, would prefer that the champion take part in a tournament.
The women's championship (also played this month) does feature a tournament. 64 players were seeded, and played single-elimination two-game matches (with rapid games as tiebreakers). The final two players then faced each other in a four-game match (again with rapid games as potential tiebreakers). The final did go to tiebreaks, and was won by defending and now repeat champion Ju Wenjun.
Edit: I suppose that makes sense to encourage more women to play if that was an issue. (I'm used to more casual clubs where membership requires only interest and showing up.)
In lieu of such data, a simpler explanation is that boys are more encouraged to play chess from a young age than girls. This results in more teenage boys playing chess, a deeper talent pool, and thus better top ranked players.
This is similar to what is seen in soccer. Even though China has much bigger population than Holland by almost 100x, the number of Chinese kids playing organized soccer is less than Holland by at least 10x.
https://www.sciencemag.org/news/2017/04/study-finds-some-sig...
> “[That previous study] finds no average difference in intelligence, but males were more variable than females,” Ritchie says. “This is why our finding that male participants’ brains were, in most measures, more variable than female participants’ brains is so interesting. It fits with a lot of other evidence that seems to point toward males being more variable physically and mentally.”
So if you’re looking for outliers (such as a chess prodigee), you are more likely to find them in the male population than in the female population.
Your explanation is not simpler by any stretch, it just spares you some cognitive dissonance.
Which naturally raises the question of whether they can be manufactured. And, regardless of how you may feel about the ethics of testing that experimentally, László Polgár tested it in order to explore his idea that "geniuses are made, not born". The result of his experiment:
* Oldest daughter Susan (Zsuzsanna) achieved Grandmaster at age 22. Peak rating 2577.
* Middle daughter Sofia (Zsófia) achieved International Master, peak rating 2505.
* Youngest daughter Judit achieved Grandmaster at age 15 years 4 months, at the time youngest person ever to do so. Peak rating 2735, ranked #8 (not "women's #8", worldwide #8).
Imagine they also tie all their matches; now the world has four reigning chess champions!