Science says trans women can't jump:

https://bjsm.bmj.com/content/early/2024/04/10/bjsports-2023-108029

(not resolving because it's one small-scale study and the evidence is indirect, but this study seems evidence for a small disadvantage (going from weight to height reduces the difference, but it doesn't invert it)).

FWIW the consensus opinion of HS coaches all sports, and officials specifically volleyball at HS level, whom I know -- trans kids are not usually above average players. Heavy enough lift for cis girl athletes to manage expectations/presentation of their bodies and hair and style before even factoring in how to do all that when you didn't grow up with it. How that translates to the highest levels I have no idea But 99.999 percent of sport is not played at the highest levels. Giving precious brainpower to the potential effect of the occasional trans woman high-level athlete on the whole sport? For perspective, we are not talking multi-million TV rights here. It's volleyball. A sport where controversy ensues if you wear a bikini or not. What information are you giving the world about yourself by choosing this as something to chew over in public?

@ClubmasterTransparent

What information are you giving the world about yourself by choosing this as something to chew over in public?

Please don't be passive aggressive. What information do you believe you have gained about me because I submitted this question?

@ClubmasterTransparent But being less lazy about my answer, transgender sports seems to be at risk of turning into a sort of societal double crux. The left-wing position seems to be logically reducible to

Trans rights => trans integration in sports is good

but this implies

not(trans integration in sports is good) => not(trans rights).

which would be bad to see happen.

Personally, I would like trans rights to be supported even if there is an 'unfair advantage' in sports, so for me it is important that we figure out whether trans integration in sports is good before pro-trans movements put too many eggs in that basket to get mad over spilling.

I also agree with your argument that most sports matches aren't serious enough to warrant exclusion, and honestly I'd argue that even in top-level competitive sports a 15cm-equivalent advantage would just be a 15cm-equivalent advantage, and even in this scenario it makes as much sense to ban a 195cm tall trans woman from competing as it makes sense to ban a 210 cm tall cis woman.

I am genuinely confused why you're not voting down the >10cm option given your comment when it's an 80% increase in mana invested if you bet it down to 10% and it resolves NO.

And I'm still curious what information you believe you gained about me.

@dph121 Thank you for thoughtful answer. I wrote that comment the morning after a dinner out that was seriously marred (including for others beyond our table!) by a big rant on the subject. I hope I'd have taken a different time another time or not been moved to comment at all. I apologize for the way it landed.

I agree good odds. This bet would not have fit with my overall strategy though. Which I am trying to be more disciplined about.

It is the combination of height and vertical jump which provides advantage in volleyball. Men have substantially higher vertical jumps than women, especially among athletes. In my personal experience playing high level volleyball, the difference in jumping ability is much, much larger than 10cm. Likely closer to 30cm. A cis woman needs a lot of extra height to make up for this.

And then once you are up in the air, it is upper body strength that matters. A cis woman is going to need an additional height advantage to compete against the trans woman's substantially higher upper body strength.

@KevinCarlton I'm proud to announce that science says trans women can't jump.

Trans woman athletes jump worse than cis woman athletes even before compensating for cis woman athletes being shorter:

(NB: the right graph uses weight, but the difference in weight between cis and trans women seems greater than height would explain even if the Benn parameter was 3).

Upper body strength isn't measured and they do find trans women have higher absolute grip strength, though I would guess grip strength is related to height in the same way pliers are more effective with a longer handle, in which case grip strength would not have statistically significant difference.

Assuming the UK standard height difference of 14 cm, a standing trans woman would have 18 cm higher reach. According to this website, volleyball jumps for top level cis women get 80-100 cm of vertical height, while the jump in the study had restricted movement and reached 40 cm. Assuming that the people tested could jump 1½ times as high with a full run-up, that means a 11 cm difference in volleyball jump height in favor of cis women. This means cis women would get 7 cm less vertical reach despite being 14 cm shorter on average.

So if I had to resolve based just on this study, I would pick a 2.5-10 cm disadvantage for trans women.

The sample size is small and the evidence is indirect, but given you care so much about jump height this seems worth updating on.

It seems plausible to me that this would depend significantly on the actual skill level of the players. An extreme example would be people who have never played before. Within the normal range I suspect height matters a lot less there, because the outcome is more ~random anyway, and you wouldn't know how to make good use of the height advantage.

If research like this is done, I doubt it would on people who haven't played before, but that still leaves a fairly wide skill range.

@jskf Good point. I updated the description: if height matters differently at different skill levels, I'll go with the highest level for which there is credible evidence.

Anecdotally, height is pretty useful at a beginner level because unskilled flailing has a higher chance of hitting the ball and because you can block and spike more easily at the net. I would expect height to become a less significant factor as skill also begins to contribute.

Like, suppose a ball passes 2.20 meters above the floor over a player's head. An unskilled player with a jumping reach of 2.25 meters would have to time her jump just right to hit it, while an unskilled player with a jumping reach of 2.40 meters has a much longer interval to hit. Meanwhile skilled players would understand the timing so both the player with a reach of 2.25 meters and 2.40 meters could hit the ball every time.

@dph121 Interesting, that makes sense. You may have guessed that I know absolutely nothing about volleyball. Do you know in what way people are suggesting being transgender is a big advantage? Strength?

@jskf actually I guess I'm more interested in what you think would be most likely. People who are mad about this kind of thing aren't always super interested in figuring out what's actually true lol.

@jskf I don't really know either, so this is my attempt at outsourcing the research. As far as I can tell the main argument right now is that there hasn't been any evidence of a significant difference, which makes obvious differences unlikely. But with the current state of acceptance, a lot more raw data will become available and people will become more interested in research, so differences hidden by noise could be revealed.

There are arguments about how differences in skeletal shape or residual muscle might give people that had a testosterone puberty an advantage, or how bone density might give people on hormone replacement therapy a disadvantage, but I've only seen them used as Arguments as Soldiers rather than in an objective context.