In this generous season, consider the greatest gift we regularly and personally give (even if we do not intend it as such): sex.  Back in 2005, Tyler Cowen pondered Michael Vassar’s pregnant observation: "there is an inexplicable shortage of sex."  This remains, I think, one of the most neglected questions in social science.  We should devote far more effort to diagnosing and fixing this problem.  To inspire more precious gift-giving, let us review the health benefits of sex [as of 2003]:

Saving yourself" before the big game, the big business deal, the big hoedown or the big bakeoff … there’s no evidence it sharpens your competitive edge. The best that modern science can say for sexual abstinence is that it’s harmless when practiced in moderation.

In one of the most credible studies … tracked the mortality of about 1,000 middle-aged men over the course of a decade. … Its findings, published in 1997 in the British Medical Journal, were that men who reported the highest frequency of orgasm enjoyed a death rate half that of the laggards. … In a 2001 follow-on … by having sex three or more times a week, men reduced their risk of heart attack or stroke by half.

Sex, if nothing else, is exercise. A vigorous bout burns some 200 calories–about the same as running 15 minutes on a treadmill or playing a spirited game of squash. … Sex also boosts production of testosterone, which leads to stronger bones and muscles. …

A 2002 study of 293 women … reported that sexually active participants whose male partners did not use condoms were less subject to depression than those whose partners did. One theory of causality: Prostoglandin, a hormone found only in semen, may be absorbed in the female genital tract. …

Immediately before orgasm, levels of the hormone oxytocin surge to five times their normal level. This in turn releases endorphins, which alleviate the pain of everything from headache to arthritis to even migraine. In women, sex also prompts production of estrogen, which can reduce the pain of PMS.  …  individuals who have sex once or twice a week show 30% higher levels of an antibody called immunoglobulin A, which is known to boost the immune system.  …

Better teeth: Seminal plasma contains zinc, calcium and other minerals shown to retard tooth decay. Since this is a family Web site, we will omit discussion of the mineral delivery system. …

A study recently published by the British Journal of Urology International asserts that men in their 20s can reduce by a third their chance of getting prostate cancer by ejaculating more than five times a week. … Erectile dysfunction … may be telling you that you have diseased blood vessels elsewhere in your body. … "Men who exercise and have a good heart and low heart rate, and who are cardio-fit, have firmer erections. There very definitely is a relationship."

But is there such a thing as too much sex?  The answer, in purely physiological terms, is this: If you’re female, probably not. If you’re male? You betcha.  … Regular sessions can not only firm a woman’s tummy and buttocks but also improve her posture … [though] sometimes you can have a lubrication problem.

Women who abstain from sex run some risks. In postmenopausal women, these include vaginal atrophy.  … As for men, urologist Eid says it’s definitely possible to get too much of a good thing, now that drugs such as Viagra and Levitra have given men far more staying power than may actually be good for them.

Tyler discussed several theories of why we have too little sex.  I also ponder why we neglect this as a research topic.  It seems to me that enjoyment of sex is seen as a "silly" topic, not worthy of "serious" researchers.  So Kinsey is one of my heros.