I work in STEM academia and the sex pay gap is around 7%. It’s a little more nuanced than outright sexism though.
Females and males get paid exactly the same for the same job. Pay scales are public and anyone can look up someone’s salary.
We are banded into categories containing several salary points, and you move up a point each year. So you can have Lecturer 1 paid more than Lecturer 2, if Lecturer 1 has been employed longer with no employment gap.
We have a very generous maternity package so females are more likely to take longer leave.
This means females are more likely to occupy the lower salary points within a given category - they are more likely to be Lecturer 2. Thus, it could seem that female lecturers are paid less than male lecturers.
Of course, academia is also overwhelmingly male at the top, where the max salaries are, which is probably a bigger skew.