For those who write about rape, it's rare to be called upon to cover good news. However, a new report in USA Today would seem to be precisely that: the rates of reported rape are lower than they have been in 20 years.

Just because rape is less frequent, however, does not necessarily mean that it's actually rare. The report states that 89,000 women reported being raped in 2008. This is down from 109,062 reported rapes in 1992. The difference, from this year to that, is a drop of only about 18%. And, when we consider that rape continues to be underreported – statistics available at the Rape, Abuse and Incest National Network (Rainn) state that about 60% of all sexual assaults aren't reported to the police – we're looking at much higher numbers.

And then there are sexual offences that are not rape but are often no less damaging: all of the forced, coercive, abusive sexual encounters that don't fit the precise legal definition of rape and generally fall under the heading of "sexual assault". That, too, takes the number up. According to Rainn, there were 248,300 victims of rape and sexual assault in 2007, not including victims younger than 12. There's no question that sexual assault continues to be a serious problem. Still, when we see a decline like this, it's worth our time to ask what caused it.

The USA Today article credits several concrete factors: increased funding for rape prosecutions through the Violence Against Women Act, advances in DNA testing that make it easier to convict rapists and the widespread availability and use of rape kits that collect evidence after the fact. But they also credit shifts in the culture, including increased awareness of rape and decreased tolerance both for sexual assault and for lines of thought which minimise it, excuse it or place the blame for it on its victims.

This last point is the most crucial. And it's important not to overstate the progress that has been made, as Michael Males, of the Centre on Juvenile and Criminal Justice, does in the article: "You don't see the nightmarish trials of the 1960s where a woman's reputation would be brought into question and people would conclude she deserved it."

That would be a marvellously uplifting statement, were it not also blatantly untrue. Women who take their rapists to court are still routinely blamed and denigrated, either by defence attorneys or by onlookers, and there are still some who argue that preventing rape is somehow inherently the victim's responsibility.

Yet there is one difference between the victim-blaming of the 1960s and the victim-blaming of today: Nowadays, people know what to call it, and are willing to challenge it publicly. "Victim-blaming" itself, once regarded as a strange and radical theory – what do you mean, the fault for rape lies with rapists? – is now a central part of our understanding of sexual assault and the culture surrounding it. This doesn't mean that it has stopped happening. It means that, when it does happen, people are able to identify and resist it.

And this is the entire history of feminism and anti-rape activism: the history of people introducing ideas that are seen as prudish and crazy and extreme until they are understood as common sense. Or, in some cases, law.

Here's a history of some of the crazy ideas advocated by the feminist fringe: that rape is still rape if you were dating or married to your attacker, since knowing or even loving someone does not necessarily make it impossible for that person to hurt you. That a woman's prior sexual history should not be used as evidence against her in a rape trial, since having consented to sex in the past does not mean that you have implicitly consented to all sex thereafter. That rape is still rape if a woman does not or cannot physically resist her attacker, since it is generally unwise to require that all rapes come with an accompanying beating. That some rapists use no physical force whatsoever, and employ intimidation, coercion or intoxication as weapons, and that it is still rape if compliance is forced through these measures.

All of these ideas were once radical. Indeed, there are still many people who regard some or all of them with deep hostility. But most of them have become central to our understanding of sexual assault, and that understanding is often reflected in the changing rape laws of the last 40 years.

Rape has always been a hot-button issue. No politician or judge in his or her right mind would take a pro-rape stand, now or in 1962. But this hasn't stopped some of them from taking stands that are, in fact, pro-rape, whether due to poor understanding of the issue or bad priorities. Consider the amendment to the defence appropriations bill recently passed in the Senate, which would cut the funding of defence contractors if they do not allow their employees to take rape cases to trial. The amendment was inspired by the case of Jamie Lee Jones, who was gang-raped by her Halliburton co-workers in Iraq, and was prohibited by the terms of her employment contract from taking legal action. It seems like eminently good common sense. Yet 30 Republican senators voted against it, and one, Jeff Sessions of Alabama, called it "a political attack directed at Halliburton." I don't doubt that Senator Sessions, if asked, would say that rape is generally a bad thing – but not as important to him as maintaining partisan boundaries, it appears.

In general, however, US society has gotten better at identifying and fighting rape, simply because more of us now know what it is and understand its seriousness, and fewer of us are willing to write it off as an awkward and unpleasant part of relationships or sex in general. And without people to challenge the common understanding of "sex in general," this would never have happened.

It appears that the percentage of rape victims who report their rapes has grown slightly higher (61% of rapes are unreported now, as opposed to 69% in 1996) even as the number of reported rapes has substantially dropped. Though we may be sceptical of reports that claim total, unmitigated progress, it can't hurt to take stock of the progress we have made.

The ceaseless work of anti-rape advocates has resulted in more survivors willing to name and oppose rape. And it has also resulted in the fact that people in general are now able to recognise which actions qualify as rape, and are willing to refrain from those actions or condemn them when they are undertaken by others. We demanded that people understand rape as a crime and treat it as such. And we are getting exactly what we asked for – not as much of it as we want, and not as quickly as we want, true, but we are getting it nonetheless.

It's certainly true that feminists and anti-rape activists did not make this happen by congratulating themselves on their accomplishments or being purely, mindlessly content with various minor advances in the status quo. They got it by being relentless, demanding, thick-skinned and willing to challenge conventional wisdom about rape and consent whenever possible.

Giving up now, or concluding that the battle is won, would be ridiculous and counterproductive. But it is worthwhile to note that we are, in fact, winning. If nothing else, it bolsters one's willingness to go out there and demand better from the world.