Well, I'm assuming "applicant pool" means the pool of all people applying. My point was that even if women are a small portion of the applicant pool, they may represent a larger quality-weighted portion of the total applicant pool. I agree that if as your population becomes large, you should asymptotically be approaching the demographics of your quality-weighted applicant pool.

Note: By "quality-weighted" I really mean something more complicated like "ROI-weighted", since it could also be that because of your reputation as a "female-friendly" employer, high-quality female employees will be willing to work at a lower salary than they would otherwise demand at a "male-dominated" workplace (e.g. "Well, company X pays better, but I really like the culture/people/policies at company Y...")