There's a case currently in front of the employment courts here in NZ which is confronting this directly. A group of aged-care nurses (working in retirement homes etc.) have made a claim to the employment court that (a) it's a female-dominated vocation, (b) it's lower paid than other similar vocations (by demands, skills, qualifications etc) and (c) that (a) and (b) are linked.

The case has made it through preliminary hearings and is now proceeding to a higher court; if they win a massive precedent will be set, allowing for claims of gender discrimination at the level of entire industries and vocations.

(I think it's totally a fair claim.)