My thesis on female sexual behavior is this: 'Women's unwillingness to
have sex, where men would be willing, is a function of their
perception of the benefits to be obtained by withholding it.'. It must
be understood that: this process by which women decide is largely
unconscious, that the benefits stated are not necessarily financial,
and that they are not just obtainable from _that man_ they are
considering but from all men perceived to be in the same group.

Examples of this principle's success are the following:

1. Young girls (middle school to high school age, but past puberty)
that are sexually active at all often have boyfriends the same age
that are not employed and supported by their parents (like all
children). Adult women generally would not consider a man that is
unemployed and supported by his parents, even if she is.

Explanation: The 14-year-old girl has no realistic prospect of getting
a lover the same age that can support her, therefore does not get that
benefit by withholding sex. The adult woman does.

2. In confined environments women are more willing to have sex with
peers regardless of whether they would be suitable outside.

The high likelihood of sex is, after all, why prisons (and similar)
are segregated. The military is not segregated now, and sex happens as
much as you could imagine. The high rate of pregnancies in the
military, especially the Navy, is not solely due to the benefits
offered to women that become pregnant as women rarely are willing to
have sex to achieve pregnancy when they would not otherwise desire sex
(if they were, child support would ruin men much more than it actually
does!).

Explanation: The woman at that point has little to no possibility of
getting a more
suitable man, and therefore her sexual desires are satisfied with what
is available.

3. Women are sexually looser with travelers and foreigners than they
would be with men from home. For white women in the Western world,
this interacts with dogma against 'racism' to cause it to also include
men of other races.

Explanation: Those men belong to a class that are not likely to commit
the same way as domestic men anyway, and therefore deny women the
benefits of withholding sex. Men of other races can be perceived to
belong to that class, because for almost all of human evolution, men
looking that different were foreigners.

4. Conversely, women traveling to another city, or more, to another
country, are more likely to have an affair there than to have one at
home.

Explanation: The same, essentially. This is further augmented if the
women is already married or in a committed relationship at home (see
next).

5. Women that are married or in committed relationships, especially
after long enough to get over the stage of initial infatuation (a few
years), may have affairs with men that would never be considered as
partners were they single, such as, most evidently, men that are poor
or of a lower social class.

Explanation: Being in a relationship that satisfies, at the moment, a
woman's financial demands, as well as being legally or emotionally
difficult to escape from, causes a woman not to perceive any benefit
by refraining from sex outside it.

6. The previous is especially true for women that are wealthy, and may
be true for independently wealthy women that are single.

Explanation: Wealth reduces the incremental benefit obtainable from
any sexual relationship.

7. The previous does not usually apply to women working for a living:
no matter how much money they are making, they usually concentrate
exclusively on men making as much or more.

Explanation: Working for a living causes one to _feel_ financially
insecure, no matter how much money one actually has.

8. The availability of prostitution in a society is negatively
correlated with men's ability to find normal sexual relationships that
are not prostitution.

Explanation: Prostitution increases women's ability to withhold sex
and not have the man lose interest, because he can be satisfied that
way. Thus, the balance is tipped against men.

9. Women sometimes enter into sexual relationship with teenage boys,
despite having access to adult companionship. That the most notorious
cases involve school-teachers is a combination of such being more
newsworthy, more likely to be discovered, and those women simply
having the most access to men in that age range.

Explanation: A combination of 5 and 1 (the male is seen as a member of
the group of teenage boys).

10. Women are more attracted, all else equal, to men that are already
getting more female attention, and in a relationship with them will
put up with poorer treatment than from an equivalent ordinary man.

(Partial) Explanation: Such a man is going to have adequate sexual
satisfaction no matter what, so withholding sex from him will
typically avail less.

I hope this list has been more convincing than my original post. You
may have the reaction that many of these points are 'obvious'. But I
am not discussing how well known they are, I am discussing WHY they
are.