[Aperson4321]

I am not an expert and I don't have the numbers, but not all "gifted" are talented in mathematics. Also the study of the field of mathematics is a task of endurance and slow but steady work, this is something the highest tier gifted (profoundly gifted) tend to suck at even with proper disipline training, but the profoundly gifted is so few in number that they don't really have an effect on the percentage.

Gifted often have one or more of the five overexcitabilities, one of those are Intellectual overexcitability, one can guess that a notable part of gifted who participate got Intellectual overexcitability, then you can make a guess that ca 20% of gifted got Intellectual overexcitability, that 50% fail to get that far in school because of the problems gifted face, then 30% from those gifted living in shitty enviroments that stops them from learning about the joy of mathematics and then 50% of those in turn actually puts in the time to learn mathematics, then 25% is actually good enough to enter so maybe: 0,375%

The education system really sucks for gifted kids, especially highly giften, exceptionally gifted and profoundly gifted, the mildly gifted and moderately gifted can be helped alot by the imperfect solution of being moved up a few classes.