Pornography. Most people have seen it, and have a strong opinion about it. Many of those opinions are negative—some people argue that ready access to pornography disrupts social order, encouraging people to commit rape, sexual assault, and other sex-related crimes. And even if pornography doesn’t trigger a crime, they say, it contributes to the degradation of women. It harms the women who are depicted by pornography, and harms those who do not participate but are encouraged to perform the acts depicted in it by men who are acculturated by it. Many even adamantly believe that pornography should become illegal.

Alternatively, others argue that pornography is an expression of fantasies that can actually inhibit sexual activity, and act as a positive displacement for sexual aggression. Pornography offers a readily available means of satisfying sexual arousal (masturbation), they say, which serves as a substitute for dangerous, harmful, and illegal activities.

Some feminists even claim that pornography can empower women by loosening them from the shackles of social prudery and restrictions.

But what do the data say? Over the years, many scientists have investigated the link between pornography (considered legal under the First Amendment in the United States unless judged “obscene”) and sex crimes and attitudes towards women. And in every region investigated, researchers have found that as pornography has increased in availability, sex crimes have either decreased or not increased....