At what age are 95% of people mentally able to give consent?

People under the age of consent still lack the mental ability to give informed consent. but the age of consent varies across countries and states from puberty in Yemen to 15 / 16 / 17 / 18 ( France, UK, Ireland, Tunisia).

can the mental ability to give consent be scientifically defined / measured /approximated?
if yes, at what age are 95% of people mentally able to give consent? or more ideally what’s the percentage of people mentally able to give consent in function of age.( does it follow an S-curve? )

Does that age vary across cultures / countries / education systems?

** ( of course, other factors come into play in determining the legal age of consent like the economical dependence of teens and tradition) but if less than 95% of people of certain age are unable to consent, one might argue that, that age is too low.