Rules of thumb, based partly on research, but not from any book:
The incidence of sins against the flesh involving another person, between men and women, is roughly equal. That is, per 100 sins of flesh committed, half are by a woman and half by a man. However, the prevalence of sinners against the flesh is not equal. More men, at some point in their life, have committed sins against the flesh (in all categories). Fewer women have. The women that do, however, tend to be more promiscuous than men. This is shown in scientific research on sɛҳuąƖly transmitted disease, and also in confidential/anonymous interviews.
A quote from the Summa (which I respect greatly, but in which it is still possible that factual errors exist) given by Telesphorus :
...however, other things being equal, a man sins more grievously in simple fornication than a woman, because he has more of the good of reason, which prevails over all movements of bodily passions
A man sins more grievously in many things, but the above statement is applied incorrectly to fornication, because it is an exception:
Research conducted in the past 10 years has shown that in circuмstances where a man or woman is presented with a person of the opposite sex that he or she finds attractive, the man's ability immediately thereafter to make rational decisions, such as those based on money, are impaired, whilst the woman's is not.
Therefore, it could be said that when a woman sins in fornication and adultery, it is
she who is the more grievous sinner (on balance). A man's brain turns to mush when he is attracted to a woman, but a woman is still cool and calculating. This is a generalization, but as a rule it is correct. A woman can simply say no, if she so decides. A man can be turned much more easily.
I am not sure what the statistics are on whether women are more likely to fornicate or commit adultery, or the same for men. It could be inferred from statistics of women having abortions or taking contraceptives, but otherwise I don't know.
As for divorce, women are by far the majority of those who initiate it. Men are often completely oblivious that a divorce is coming. Again I would argue that women are more often the wrongdoers, and ironically the divorce courts are stacked with feminists.