Has one in every ten women really been raped?

Another online survey, this time from Mumsnet, concludes that one woman in ten has been raped, and over a third have been sexually assaulted. The best data we have, from the British Crime Survey, suggests this is an overestimate.

The latest bulletin on Homicides, Firearm Offences and Intimate Violence, published in January, indicates (Table 3.01) that 3.7 per cent of women report having been raped since the age of 16 (4.5 per cent if attempted rape is included), and 18.6 per cent report having experienced any form of sexual assault – around half the proportions reported by Mumsnet.

The BCS figures come from a properly-chosen sample of more than 6,000 women. The Mumsnet results come from “write-in” responses on its website from 1,609 women.

There are differences in coverage: Mumsnet included in its responses all rapes and assaults over a lifetime, while the BCS counts only those occurring over the age of 16. That could account for some of the difference, but a more likely explanation is that the Mumsnet respondents are not a representative sample, being overweighted by those who have suffered abuse.

The Mumsnet survey is part of a campaign called We Believe You. I certainly don’t disbelieve Mumsnet’s respondents, as it’s unlikely they are making it up. But I don’t believe that any self-selected survey of this sort provides a basis for reaching any conclusion at all.

Among those who said they had been raped or sexually assaulted in the Mumsnet survey, only 9 per cent said that they had reported the assault to the police, against 29 per cent of women in the BCS survey who said that they had reported partner abuse to the police in the past year. Yet a majority of the Mumsnet respondents (59 per cent) also believe that the police are “quite” or “very” sympathetic to women who report rape. So why not report it?

The survey was widely but not universally covered – The Times and The Guardian did not report it, but The Independent, The Daily Telegraph and The Sun did. The BBC reported it at length, but without challenging the Mumsnet figures. Doesn't the BBC College of Journalism include a course on statistical scepticism?

Casting doubt on the Mumsnet claims does not imply any lack of sympathy for victims, or a failure to accept the scale of the problem – just a desire to anchor policy on the best evidence available, which this isn’t.