I am speculating here, but maybe, if a woman's spouse happens to be working, the woman will not be counted. Or who could be counted as having an early pension? Who is registered to receive benefits from the state under which conditions? Does voluntary work make one disappear from these lists?
There are other unemployment numbers that include people who would work if offered a job but aren't actually looking for one, but that's not the main measure that BLS uses. People that wouldn't take a job even if you offered one to them (like students and early retirees) don't count at all- they don't even show up in the denominator of any of these measures. BLS has the summary of all 6 measures of unemployment at http://www.bls.gov/news.release/empsit.t15.htm but I don't think they have the detailed breakdown of any of the other measures.
You have to be in the workforce to be reflected in them. Voluntary work doesn't count -- and in many cases women are caregivers for grandchildren, spouses, older parents, etc.