In the 1980s, conservatives and feminists joined to fight a common nemesis: the spread of pornography. Unlike past campaigns to stamp out smut, this one was based not just on morality but also on public safety. They argued that hard-core erotica was intolerable because it promoted sexual violence against women.
"Pornography is the theory -- rape is the practice," wrote feminist author Robin Morgan. In 1986, a federal commission concurred. Some kinds of pornography, it concluded, are bound to lead to "increased sexual violence." Indianapolis passed a law allowing women to sue producers for sexual assaults caused by material depicting women in "positions of servility or submission or display."
The campaign fizzled when the courts said the ordinance was an unconstitutional form of "thought control." Though the Bush administration put new emphasis on prosecuting obscenity, on the grounds that it fosters violence against women, pornography is more available now than ever.
That's due in substantial part to the rise of the Internet, where the United States alone has a staggering 244 million web pages featuring erotic fare. One Nielsen survey found that one out of every four users says they visited adult sites in the past month.
So in the past two decades, we have essentially conducted a vast experiment on the social consequences of such material. If the supporters of censorship were right, we should be seeing an unparalleled epidemic of sexual assault. But all the evidence indicates they were wrong. As raunch has waxed, rape has waned.
This is part of a broad decrease in criminal mayhem. Since 1993, violent crime in America has dropped by 58 percent. But the progress in this one realm has been especially dramatic. Rape is down 72 percent and other sexual assaults have fallen by 68 percent. Even in the past two years, when the FBI reported upticks in violent crime, the number of rapes continued to fall.
Nor can the decline be dismissed as the result of underreporting. Many sexual assaults do go unreported, but there is no reason to think there is less reporting today than in the past. In fact, given everything that has been done to educate people about the problem, and to prosecute offenders, victims are probably more willing to come forward than they used to be.
No one would say the current level of violence against women is acceptable. But the enormous progress in recent years is one of the most gratifying successes imaginable.
How can it be explained? Perhaps the most surprising and controversial account comes from Clemson University economist Todd Kendall, who suggests that adult fare on the Internet may essentially inoculate against sexual assaults.
In a paper presented at Stanford Law School in 2006, he reported that, after adjusting for other differences, states where Internet access expanded the fastest saw rape decline the most. A 10 percent increase in Internet access, Kendall found, typically meant a 7.3 percent reduction in the number of reported rapes.
For other types of crime, by contrast, he found no correlation with Web use. What this research suggests is that sexual urges play a big role in the incidence of rape -- and that pornographic websites provide a harmless way for potential predators to satisfy those desires.
That, of course, is only a theory, and the evidence he cites is not conclusive. States that were quicker to adopt the Internet may be different in ways that also serve to prevent rape. It's not hard to think of other explanations for why sexual assaults have diminished so rapidly -- such as DNA analysis, which has been an invaluable tool in catching and convicting offenders.
Changing social attitudes doubtless have also played a role. Both young men and young women are more aware today of the boundaries between consensual and coercive sex. Kim Gandy, president of the National Organization for Women, thinks the credit for progress against rape should go to federal funding under the Violence Against Women Act and to education efforts stressing that "no means no."
But if expanding the availability of hard-core fare doesn't actually prevent rapes, we can be confident from the experience of recent years that it certainly doesn't cause such crimes. Whether you think porn is a constitutionally protected form of expression or a vile blight that should be eradicated, this discovery should come as very good news.