The joy of stats

70% of women married for more than five years were having affairs 25% of 13-to-18-years-olds say they have sent a sexual image 34% of women report a lack of interest in sex lasting at least three months in preceding year

We’re all having sex a lot less. Finns have a thing for handcuffs. And if you’re a 60-year-old virgin you’re not that unusual in Ireland. At least, that’s what the statisticians would have you believe...

large, the less sexually easy-going you are, the less you will be inclined to answer questions about your sex life. This bias towards the uninhibited reached a particularly absurd height in Shere Hite’s surveys into sexuality in the Seventies and Eighties. Hite distributed 100,000 sex questionnaires, from which she received only 3,019 replies, or just over 3%.

Quite clearly, this 3% would consist of the most raunchy and the most aggrieved. It’s easy to imagine Mrs Robinson from The Graduate, or Mildred from George And Mildred, avidly filling in her Shere Hite questionnaire. Small wonder, then, that Hite discovered, among much else, that 70% of women married for more than five years were having affairs, and that 95% reported ‘emotional and psychological harassment’ from their partners. The chairman of the Harvard department of statistics concluded that the Hite Report was ‘not representative of any group except the odd group that chose to respond’.

In even the most responsible sex surveys, heterosexual men report having had more partners than women ever do: the most recent showed that men report an average of nine partners over a lifetime, while women report only five. Yet, logically, the average number of partners over any period of time must be exactly equal for men and women.

It turns out – well, I never! – that men exaggerate while women underestimate; also, men are happy to include events that women would prefer to forget. In one test, in which female students were asked how many people they had slept with, a third were told their questionnaire would be seen by a supervisor, a third were guaranteed anonymity, and the final third were told they were being attached to a lie-detector. The first group claimed an average of 2.6 sexual partners, the second ‘anonymous’ group said 3.4 and the lie-detector group said 4.4.

In many ways, Sex By Numbers is more about numbers than about sex. Every now and then, the author makes rather heavy-handed jokey references to sex –the book is dedicated, off-puttingly, to ‘everyone in history who has struggled with sex. And eventually called it a draw’ – but his real interest lies in all the different statistics, and whether or not they stand up to scrutiny.

Some do and, of these, quite a few are pretty surprising. The more older brothers a man has, the more likely he is to be gay. In 1938, half of brides in England and Wales were pregnant when they got married. Gays are a third more likely than heteros to be left-handed. And, possibly the most useful fact of all, to keep your cut-flowers erect for longer, try Viagra.

‘It turns out–well, I never– that men exaggerate while women underestimate their number of partners’