Rapes and attempted rapes have declined in the United States, and sharply, over the past 30 years, according to the government’s most painstaking crime survey. A second big government tally finds the same trend but a gentler decline.

If they’re right, the recent spate of stories about alleged rapes, whether true or false, obscures the fact that sexual crime is on the wane. The decline, in the view of one top criminologist, James Alan Fox of Northeastern University in Boston, is part of a widely documented drop in violent crime in the United States over the last 12 years.

Fox credits more police attention, a sensitized public, demographic changes and some effective new government programs for the decline in rapes, which he calls “a pretty dramatic trend, actually.”

However, the picture is more depressing on college campuses. Among college women, “the problem is as serious as it’s ever been,” said Peggy Reeves Sanday, an anthropology professor at the University of Pennsylvania in Philadelphia.

She and others who focus on college campuses find high and steady abuse rates among young women over the last decade. Those numbers reflect a definition of abuse that includes nonconsensual sex in the haze of alcohol, as well as psychological and physical pressure. That definition wasn’t widely used in surveys before 1986 and is broader than what government surveys use.

Sexual-violence rates remain highest among women ages 20 to 24, according to the Justice Department’s latest annual National Crime Victimization Survey. It estimates that rapes and attempted rapes in the United States fell more than 80 percent from 1973 through 2004. That amounts to a drop from 2.5 per thousand per year to 0.4 per thousand.

The study began tallying fondling, molestation and other forms of sexual assault only in 1993. The rate at which they’re reported is down about two-thirds since then, from 1.6 per 1,000 to 0.5.

The annual survey, which the Census Bureau conducts with mainly female interviewers, counts heterosexual and homosexual assaults on males or females 12 and older. Ninety-seven percent of those who reported attacks in the latest survey were women. The study is designed to pick up trends for all kinds of crimes, not just rapes.

The most recent results are based on interviews of 74,520 people in 42,000 households. The response rate approaches 90 percent, thanks to repeated attempts to make contact and the emphasis on home visits. It comprises sexual violence that is and is not reported to police.

Criminologists don’t consider the victimization survey an accurate measure of how many rapes occur, because many – and probably most – incidents of sexual violence go unreported, even to the surveyors. Rather, its numbers are viewed as indicative of long-term trends. Reductions since 1973 in the size of the study’s still-massive sample and budget cuts have made the survey even less definitive, criminologists say. But it remains the essential measure when it comes to national trends in sexual violence.

“It’s the best we have,” said Sam Walker, a criminologist at the University of Nebraska at Omaha, citing the study’s high response rate, painstaking methodology and relative consistency over many years.

A second national survey, the FBI’s Uniform Crime Report, which is based on arrests reported by 17,000 police agencies nationwide, found a 13 percent decline in forcible rape, attempted forcible rape, assault with intent to commit rape and statutory rape since 1991.

Because women today are more likely to report sexual violence to police, according to research by criminologist Eric Baumer of the University of Missouri-St. Louis, the FBI’s arrest numbers for rape would rise if they weren’t offset by declines in sexual violence, Baumer thinks. Instead, the FBI’s 13 percent figure “understates the decline,” he said.

Why is sexual violence declining?

“We really don’t know,” said Baumer, who’s been studying the question. He thinks it’s a combination of factors, some of them affecting just sexual violence and others contributing to the overall decline in violent crime.

A study of violent crime’s decline by the Urban Institute, a nonprofit Washington research center, concluded that demographics was one big factor. It found a substantial decline in the ’80s and ’90s in the group most likely to commit violent crimes -18- to 24-year-olds – as a percentage of the population. At the same time, middle-age adults and seniors, who are least inclined to commit violent crimes, were increasing as a percentage of the population.

Another big factor, the institute concluded, was that the U.S. prison population quadrupled in the last 25 years to 2 million. That population includes a large but unknowable number of potential rapists and of convicted rapists who would’ve been repeat offenders if they weren’t behind bars.

In the same period, groups that fight sexual violence against women won substantial victories in Congress and state legislatures. Among them:

¢ Better training of 911 operators and police – especially police dispatchers – in dealing with sex abuse complaints.

¢ More federal aid to expand local police forces, which now include more female officers.

¢ $3.8 billion spent under the federal Violence Against Women Act to provide rape crisis centers, facilitate prosecution of abusers, destigmatize acknowledgement of sexual abuse and sensitize the public to issues of sexual consent.