Image copyright Getty Images Image caption Brett Kavanaugh has denied the allegations against him

Either Brett Kavanaugh or Christine Blasey Ford is lying. We don't know which one.

Here's what we do know.

Over the past 20 years, only 2-10% of rape accusations (Prof Ford's lawyer says she believes this was attempted rape) are proven to be fake, argue the authors of a 2010 US study.

That figure does not include any unsubstantiated accusations where an investigation was unable to prove a sexual assault occurred, so an accurate figure for the total remains unknown.

Other studies have figures in the same range. The FBI has put the number of "unfounded" rapes - those determined to be false after investigation - at 8%.

Fake rape accusations get a lot of attention.

Both the Duke Lacrosse team case in 2006 and the alleged University of Virginia gang rape in 2014 were widely covered by the media. They were terrible miscarriages of justice - but they were not representative.

False rape accusations very rarely lead to convictions or wrongful jail time.

A useful article in Quartz by Sandra Newman points to research from the British Home Office showing that in the early 2000s, of the 216 cases that were classified as false allegations, only six led to an arrest.

Of those, only two had charges brought against them and those two were found to be false.

The idea that lots of men are going to prison because they've been falsely accused of rape isn't supported by that study.

Moreover, official figures suggest the number of rapes and sexual assaults which are never reported or prosecuted far outweighs the number of men convicted of rape because of fake accusations.

Indeed it far outweighs the number of fake accusations, period.

Figures from the US Bureau of Justice Statistics suggest only 35% of all sexual assaults are even reported to the police.

Image copyright Reuters Image caption Prof Ford says Brett Kavanaugh pinned her to a bed and tried to take off her clothes

It's also useful to look at what we know about the kind of people who make fake accusations to see if Prof Ford fits a pattern.

According to Sandra Newman, every academic study on the issue finds that the most common type of fake accuser is actually a teenage girl trying to get out of trouble.

Often it's her parents who report the "rape" attempt. The studies suggest the false accusation can often stem from something as absurd as finding an excuse for missing curfew.

According to a 2017 report by the US National Institutes of Health, fake accusers "were primarily motivated by emotional gain. Most false allegations were used to cover up other behaviour such as adultery or skipping school".

In many cases the fake accuser has a history of lying to authorities or committing fraud. She may well have a criminal record.

In the Duke lacrosse team case, the woman in question, Crystal Mangum, had reported a previous assault in which no one was charged.

She later faced attempted murder charges and ultimately went to prison herself over the fatal stabbing of her boyfriend.

Christine Blasey Ford clearly does not fit this profile.

She is not a teenager, she has no history of fabrications, she doesn't have a criminal record and, as far as we know she isn't trying to cover up some other behaviour.

None of this proves that Prof Ford is telling the truth but it does suggest we should be sceptical of the notion that it is common for women to say they've been sexually abused when they haven't.

It's not.

CORRECTION: This article was updated on 26 September 2018 to clarify that false accusations in the 2010 report are defined as those investigated by police and proven to be false. We have also made clear that a conclusion about the numbers of men going to prison because they had been falsely accused of rape was based on a British study. We have added links to some of the research cited.