
With Cathy's permission, I have converted the stats from this paper into graphic form.
Read on.
Delighted my research article Female Sports Participation, Gender Identity and the British 2010 Equality Act is now published in Sport Ethics and Philosophy. 1/https://t.co/wNPz2sd2WD
— Cathy Devine (@cathydevine56) November 9, 2021

Here is the data for transwomen in female sports.

SelfID would have 5 x greater effect on female tennis than on male tennis. It would have 100 X greater effect on female football than on male football.
@DavidTriesman

"Eligibility criteria based on gender identity, rather than biological sex in these sports do not therefore appear justified, balanced, or even possibly legal in Britain."
Cathy calculated the numerical impact on athlete numbers based on population data. There was, because it's tricky to work out, no adjustment for relative advantage/disadvantage in the opposite sex category.
I think the effect at the elite female level will higher.
Cathy reports, in athletics, 137400 male and 73500 female athletes. If 1.34% of males selfID into the female category, that's 1841 males from the male cohort>female cohort.

More from Emma Hilton
@Hogshead3Au @BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 OK.
Fitness data from over 85k AUS children aged 9–17 yrs showed that, compared with 9 yr females, 9 yr males were 9.8% faster in sprints, 16.6% faster over 1 mile, could jump 9.5% further, could complete 33% more push-ups in 30 s and had 13.8% stronger grip.
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Here is my full description of that data.
Example:
1.6km timed run (CV endurance)
The *best* 17 yr old girls are matched by *average* 17 yr old boys, and beaten, by some measure, by the best 9 yr old
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Male advantage of a similar magnitude was detected in a study of Greek children, where, compared with 6-year-old females, 6-year-old males completed 16.6% more shuttle runs in a given time and could jump 9.7% further from a standing
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 In terms of aerobic capacity, 6- to 7-year-old males have been shown to have a higher absolute and relative (to body mass) VO2max than 6- to 7-year-old
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Pre-puberty performance differences are not negligible, and could be mediated, to some extent, by genetic factors and/or activation of the hypothalamic–pituitary–gonadal axis during the neonatal period, sometimes referred to as “minipuberty”.
Fitness data from over 85k AUS children aged 9–17 yrs showed that, compared with 9 yr females, 9 yr males were 9.8% faster in sprints, 16.6% faster over 1 mile, could jump 9.5% further, could complete 33% more push-ups in 30 s and had 13.8% stronger grip.
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Here is my full description of that data.
Example:
1.6km timed run (CV endurance)
The *best* 17 yr old girls are matched by *average* 17 yr old boys, and beaten, by some measure, by the best 9 yr old
Here is summary data from Catley and Tomkinson, 2012, who collated performance data from 85347 Australian schoolchildren aged 9-17 years old. pic.twitter.com/qKdxqywpoq
— Emma Hilton (@FondOfBeetles) November 19, 2020
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Male advantage of a similar magnitude was detected in a study of Greek children, where, compared with 6-year-old females, 6-year-old males completed 16.6% more shuttle runs in a given time and could jump 9.7% further from a standing
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 In terms of aerobic capacity, 6- to 7-year-old males have been shown to have a higher absolute and relative (to body mass) VO2max than 6- to 7-year-old
@BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Pre-puberty performance differences are not negligible, and could be mediated, to some extent, by genetic factors and/or activation of the hypothalamic–pituitary–gonadal axis during the neonatal period, sometimes referred to as “minipuberty”.