how many people in the general population have mathematics degrees?

1.3 of undergrad degrees are in mathematics, and only about 40% of USA adults have a bachelors or higher, so about .053% of Americans have math degrees, or we can say 99.47% do not. so out of 2000 people, only 1 of them has a math degree.

Imagine being the guy who gatekeeps maths.

Except that arithmetic still qualifies as maths even if it is only barely, whereas a golf cart doesn't qualify as a sports car. It's more like saying "vehicle" when you mean "kid's bicycle "; it's still technically true even though it isn't the most sophisticated.