Only 25 percent of women are consistently orgasmic during vaginal intercourse.

This bears repeating: Only one-quarter of women reliably experience orgasm during intercourse—no matter how long it lasts, no matter what size the man's penis, and no matter how the woman feels about the man or the relationship.

This statistic comes not from just one study but from a comprehensive analysis of 33 studies over the past 80 years by Elisabeth Lloyd in her fascinating book The Case of the Female Orgasm (Harvard University Press).

Rounding things out: About half of women sometimes have orgasms during intercourse. About 20 percent seldom or ever have orgasms during intercourse. And about 5 percent never have orgasms, period.

In other words, intercourse is not the key to most women's sexual satisfaction.

Now I'm not knocking intercourse. It's central to reproductive sex. If it's well lubricated and men don't plunge in before women feel ready, it can be great fun. And it makes many lovers feel deeply connected. But contrary to what many men and women believe, and see endlessly in porn, intercourse is not the essence of lovemaking.

This statistic has several important implications:

• It's perfectly normal for women not to have orgasms during intercourse. Most women need direct clitoral stimulation to experience orgasm. They don't get it during intercourse because the clitoris is located outside the vagina and a few inches above it under the top junction of the vaginal lips. Intercourse simply does not provide enough direct clitoral stimulation to allow most women to become aroused enough to have orgasms. "Intercourse is okay," says New York City sex educator Betty Dodson, Ph.D. "But I much prefer a talented tongue on my clitoris."
• Penis size doesn't matter to most women's sexual satisfaction. If only 25 percent of women are consistently orgasmic during intercourse, then for most women, penis size doesn't matter. The fact is, any size penis can provide great pleasure to the man it's attached to. But the key to most women's erotic pleasure comes not from the penis and intercourse, but from direct clitoral stimulation, using the fingers, palm, tongue, or sex toys.
• Lasting a long time during intercourse may not matter as much as many (most?) men think it does. Why do men want to last all night? In part, because they believe it's more pleasurable for women. Many women do, indeed, enjoy extended intercourse, whether or not they experience orgasm. But only one-quarter are consistently orgasmic during it no matter how long the man lasts.
• Finally, because so few women are consistently orgasmic during intercourse, it's fine to have sex without intercourse. This is especially true for couples over 40. With age, men's erection capacity declines, and menopausal changes often make intercourse uncomfortable for women, even with a lubricant. Many older couples decide they prefer sex without intercourse. Younger lovers might also consider this erotic alternative.