Sex Drive: How Do Men and Women Compare?
How often do men really think about sex?
WSJ via Kling's summary:
... the group of people who have done particularly well from the free-marketization of sex are men high in the personality trait that psychologists call “sociosexuality”: the desire for sexual variety.
…Worldwide, there is a significant difference in average sociosexuality between the sexes, with men generally much keener to sow their wild oats than women are. The full WSJ piece is here.
I believe that most humans are highly sexual and sexually-motivated creatures. Many fantasies, if not action. It's about mostly-private thoughts. It is not as if men are always ready to go (although it is true that men are easily interested or seduced). Still, womens' sexual interests and fantasies are underestimated. Women always check out other women's clothing, but they check out men just as often.
Human biology.