So why is sexual health such a huge problem? The study suggests that unequal treatment of girls and women as the major sexual-health issue.
Some of the survey’s major findings:

While there is no major trend toward earlier sexual experience, a trend toward later marriage has led to an increase in premarital sex.
Married people have more sex than unmarried people do.
Sexual activity among single people is more common in industrialized countries than in developing countries.
First sexual experience is often forced or sold.
Monogamy is the dominant pattern in most parts of the world. Men report more multiple partnerships than do women. Such men are more likely to live in developed nations.
Marriage is no safeguard of sexual health. It is more difficult for married women to negotiate safe sex and condom use than it is for single women.
Among girls who marry at a very young age, “very early sexual experience within marriage can be coercive and traumatic.”
Condom use is increasing, but condom-use rates remain low in many developing countries.
Public health measures to improve sexual health should focus not only on individual behaviors but also on broader issues such as gender, poverty, and mobility.
Public-health messages intended to reduce sexual risk-taking “should respect diversity and preserve choice.”
School-based sexual education delays and does not hasten onset of sexual activity.
Based on the evidence they uncover, Wellings and colleagues come to what many will find to be a controversial conclusion.

“The selection of public-health messages needs to be guided by epidemiological evidence rather than myths and moral stances,” they conclude. “The greatest challenge to sexual-health promotion in almost all countries comes from opposition from conservative forces to harm-reduction strategies.”

The researchers call for providing sexual health services to unmarried young women, supplying condoms, decriminalizing commercial sex and homosexual sex, and prosecuting the perpetrators of sexual violence.

“To do otherwise will force stigmatized behaviors underground, leaving the most vulnerable people unprotected,” Wellings and colleagues argue. “Sexuality is an essential part of human nature and its expression needs to be affirmed rather than denied if public-health messages are to be heeded.”