I don't know any definite numbers (iirc its closer than 77 cents to the dollar) but in any event, a lot of the wage gap doesn't come from systematic sexism in the workplace from an employer's perspective- meaning the employer intentionally is sexist and pays women less despite having equal or better qualifications than men and/or equal/better work put in. Stigmas affecting women also come in the form of the encouragement to take lower paying jobs- not because they're lower paying, but because they're "traditional female" roles (schoolteacher, nurse, etc.) as opposed to high paying jobs that men are encouraged to take- STEM is probably the most prominent role. Women are more likely to major in humanities due to encouragement, or lower paying business majors- like Marketing as opposed to Finance. That's one reason, among others, for a wage gap.