Sex by Numbers
by Dimitra KestorasWe are all curious about how our sex lives compare with those around us. So curious, in fact, that what we’re getting up to in the bedroom is an enduring area of interest for scientists and statisticians, who put a lot of time and energy into quantifying our nocturnal behaviours. But while statistics can give us an idea, interpreting the results can be challenging. Not only is it unclear whether the answers given by study participants are reliable, but the results may not always be straightforward.
In Sex by Numbers, David Spiegelhalter considers statistics relating to a variety of topics ranging from how often people have sex to the relationship between sex and the media. We are accustomed to statistics on sex quoted out of context, usually to make you worry you’re not doing it enough or in the right way, so it is refreshing to find the origin and validity of results is assessed and analysed in depth. Spiegelhalter debunks dubious myths, including the often quoted statement that men think of sex every seven seconds, and reveals the origin of others that may be statistically sound but may not apply to the modern world. Among them is the estimate that 30% of women over 35 will never manage to get pregnant, a ‘fact’ he reveals originated 18th century France.
As well as addressing questionable statistics, Spiegelhalter explains the findings of reliable studies. He focuses on the three British National Surveys of Sexual Attitudes and Lifestyles completed to date. This is perhaps where the benefit of a statistician writing this book becomes most evident. The studies were completed in 1990, 2000 and 2010. Unsurprisingly, changes in behaviour emerge when the three surveys are compared. However, it is unclear whether sexual behaviour itself or increased willingness to report it account for these variations. For example, in 1990 only 4% of British women reported same sex experiences, in 2000 this rose to 10% and by 2010 had reached 16%. Spiegelhalter’s concise but clear explanation as to why he believes willingness to report accounted for the rise from 1990 to 2000 but change in behaviour accounted for the rise by 2010 is just one example of the ability of this book to provide an understanding of the numbers.
Aware of his readership, Spiegelhalter avoids letting his meticulous analysis become monotonous by peppering his book with interesting facts on both the statisticians who completed the studies and the methodologies they used. These include amusing anecdotes, including how three prominent statisticians found themselves singing a Gilbert and Sullivan song while waiting to meet the first American sexologist, Dr Kinsey, in 1950. He also casts a light on lesser known investigators of sexual habits that deserve greater recognition. Among them is Dr Clelia Duel Mosher, who in the late 19th and early 20th centuries challenged the view of female weakness and investigated women’s feelings about their sex lives at a time when this was not considered relevant or of interest.
Spiegelhalter addresses some fascinating questions about sex using statistics, but also takes advantage of our innate curiosity about sexual behaviour to introduce us to the strengths of statistics, and to increase our understanding of how numbers can be used to explain the world around us.
Sex by Numbers: What Statistics Can Tell Us About Sexual Behaviour by David Spiegelhalter, Profile Books and The Wellcome Collection, paperback £12.99, ISBN: 978-1-7812532-9-8
