Sex by Numbers: What Statistics Can Tell Us About Sexual Behaviour

by David Spiegelhalter

Whatever society we live in, and however open-minded we like to think we are, when it comes to our sex lives we all like to keep a few secrets. But this makes the jobs of sexologists - professionals who study sexual behaviour - pretty difficult.

Luckily, David Spiegelhalter, Professor of Risk at Cambridge University, is here to unravel the web of exaggerations, misdirections and downright lies that surround sex in modern society. Drawing on the Natsal survey, the widest survey of sexual behaviour since the Kinsey Report, he answers crucial questions such as what are we all doing? How often? And how has it changed?

Accompanying a major Wellcome exhibition on the same subject, Sex by Numbers is an informed and entertaining look at the most enduring of human obsessions, from one-night stands to the seven-year itch.

Genres: Nonfiction, Science, Psychology, Sexuality, Sociology, Adult, Relationships

368 pages, Paperback

First published April 2, 2015

About the author

Sir David Spiegelhalter has been Winton Professor of the Public Understanding of Risk at the University of Cambridge since October 2007. His background is in medical statistics, with an emphasis on Bayesian methods: his MRC team developed the BUGS software which has become the primary platform for applying modern Bayesian analysis using simulation technology. He has worked on clinical trials and drug safety and consulted and taught in a number of pharmaceutical companies, and also collaborates on developing methods for health technology assessment applicable to organisations such as NICE. His interest in performance monitoring led to his being asked to lead the statistical team in the Bristol Royal Infirmary Inquiry, and he also gave evidence to the Shipman Inquiry.

Reviews

[Simon Howard · Rating 4 out of 5]

It's not The Norm Chronicles, but it's packed with fascinating stats and has a good stab at explaining statistical concepts and research limitations in a human-interpretable way. And some of the jokes aren't bad either.

[Popup-ch · Rating 4 out of 5]

There's a lot of nonsense repeated about sex, but there are also a growing number of datasets of more-or-less reliable statistics. Spiegelhalter is a serious statistician, and approaches the subject from a numerological viewpoint, savaging dodgy statistics and teasing truths out of the more reliable records.
He grades numbers on a 0-4 star scale, with zero-star being the kind of oft-repeated factoids that 'men think of sex every seven seconds' that's complete nonsense. (In fact, some reasonably reliable studies have shown that both men and women think of sex about ten time per day, and about food more often.) Four-star data comes from official full-population reports, such as number and gender of births. From these facts lots of interesting conclusions can be drawn. For example, the gender disparity (there are more boys born than girls) has seen a curious evolution over time, with the amount of boys born increasing from a low in the mid-victorian era, and peaking during both world wars as well as in the early 1970's.

Spiegelhalter was involved in the natsal-3 survey, a serious UK-wide representative poll, that rates as three-star.

It's a shame that he hasn't made more use of the incredible amounts of data that can be gleaned from modern dating sites, as seen in e.g 'Dataclysm'.

[Aaron · Rating 4 out of 5]

A pretty fascinating read on the intersection of statistics, polling, and sexual behavior. I particularly enjoyed the discussion regarding the difficulty of polling questions regarding sex, as participants are likely to not respond or possibly lie in their responses. This creates a fascinating statistical problem. The author is English, so many of the examples come from UK governmental studies.

[Ross · Rating 4 out of 5]

A pleasing introduction to statistics and reliability, sufficient to the subject, followed by insightful description of the various study results on an obviously interesting subject.

[Ffiona · Rating 1 out of 5]

Trivializing A Serious Subject.
I do not believe the author's decision to make particular categories of sexual desires/acts a subject of statistical enquiry was based in a concern for the potentially serious consequences of sexual behaviour change for the general population. This is book written in a non serious way.It is obviously geared to appeal to readers who are already fully indoctrinated with a programmed mindset of anything goes. If you have an interest and/or preoccupation with sexual perversion this is the book for you.The author has a breezy attitude, hiding his intention to appeal to the lowest common denominator,he puts a science wrapper (charts & graphs etc) on it and then calls it fact.Stating the obvious Mr Spiegelhalter informs us...there is an increase in the spectrum of variety of sexual practices but with less frequency as apparently human sexuality has become influenced by the media and internet,our culture has intruded into our personal lives ... Who would have guessed.The author states "nature or nurture...you may believe changes in behaviour are due to a liberation that has previously been suppressed or alternatively you may believe that a new type of behaviour is being created by prevailing circumstances"

"The author asks the crucial questions what are we all doing and how has it changed?"

Unfortunately he is not able to give the readers answers to the crucial questions because of his lack of spiritual understanding about the recent radical changes to the zeitgeist ,also,no moral context is offered because he doesn't realize there is a spiritual purpose to human behaviours and human relationships.A lot of defrosting occurred in the 1960s that was supposed to guide us towards an understanding of what is called the God mind Christ consciousness etc but it all got misunderstood,went off at a tangent and warped into a permissive revolution,free love and all that haphazard hippy stuff.

The prevailing circumstances,the author seems oblivious to are....social engineering by exploiting human vulnerabilities-our children are being bombarded by an anti-God view they are literally watching hundreds of inappropriate images per hour we have allowed ourselves to become a society of desensitized programmed people,a culture drunk on its own decadence. 60 % of all internet usage is downloading porn.The decline of normal 'intimate' relating is due to people, (mainly men-studies with primates have demonstrated the increased importance of visual stimuli for males),retreating from relationships into isolated cyber fantasies,marketing loops on these porn sites are designed to appeal to specific weaknesses in the human mind so when they hit a vulnerable area the viewers arousal template is altered resulting in a warping and obsession.The capabilities of the internet when combined with human sexuality have produced an effect that has catalyzed the current dysfunctional and dangerous change in human behaviour.The normalization and cultural obsession with internet porn that has caused the change in human behaviour has a traumatic edge to it.It is a subtle sexual abuse of men, women, humanity in general really.

Western sexual mores have undergone a moral and cultural sea change,our society is now seemingly fascinated with sex.As far as I'm concerned Spiegelhalter's work is not entertaining it is disturbing because he is trifling with a serious issue.

[Daniel Gordon · Rating 4 out of 5]

I would put this book somewhere between a 3.5 and 4 star rating, but for the balanced views it maintains throughout I am inclined to say 4 stars. The author, David Spiegelhalter, works as a professor at Cambridge university, so I would expect a reliable and accurate account, even if the behaviour he is writing about is notoriously tricky to research. Sex is not only a behaviour that most people don’t feel comfortable talking to strangers about, it is also extremely variable and can be impacted by various social, political, and psychological factors. This book does a great job at providing statistics for lots of ‘general trends’ on sexual behaviour, but beyond that, as the author himself admits, statistics can fall short of capturing the sheer variability in this most variable of behaviours. If you are at all interested in the developments about how research looking at sex has changed over the years this is a good candidate. It mentions research and experiments from the past 300/400 years, with varying levels of reliability and validity (obviously).

One overwhelmingly positive thing about this book is that the author provides a star rating system for all of the statistics that he mentions throughout. This definitely helps to wheedle out the more unreliable stats and keeps things in focus. In terms of the stat I found most interesting, I would say it was that; ‘999 out of 1,000 opposite-sex acts does not lead to conception’. I knew that conceptions were relatively rare, but even I was surprised by such a strikingly low number. Also, 100,000 British heterosexual acts per minute deserves an honourable mention… The mind simply boggles, well mine did at least!

To conclude, it you are after a book about some of the really unusual aspects of sexual behaviour, such as fetishes and other odd things this probably isn’t the book for you. If however you are interested in a more balanced and impartial look at the statistics behind sex, STIs, conception, feelings about sex, how people pick partners, and how the media/social environment influence sexual behaviour this may well be the book for you!

[minney · Rating 4 out of 5]

this was really cool to reprogram my brain to understand reading graphs and numbers again !!!! i haven't done that since a-level sociology im pretty sure ! my favourite part was hearing about all the cool researchers and people who paved the way in sex studies !!!! i was extra sceptical and careful reading this because as gracie pointed out a sex book written by a man is bad news all round, im glad i read sara pascoe's sex books just before this one so i had a direct comparison between how women write about sex and how men do ? I think women just write with more compassion and kindness regarding sex. But !!! this book was super careful not to make any sweeping statements and i just liked the interesting presenting of results and hesitant conclusions drawn from really ambitious sex studies !!!! i love sexology xoxox

[RAmarl · Rating 5 out of 5]

This was a super interesting book!

The author starts by breaking down the reliability of statistics, and every time a statistic is quoted, he tells you how reliable that specific study is. I felt very comfortable with the claims made because I had all the information to make my own decision! I came away with a better understanding of how to read headlines and look deeper into them, so thanks David :)

It covers sexual behavior, pregnancy, STI's and a bunch of other stuff, and I felt like I was constantly learning. I fully recommend this book to anyone who has ever had a passing interest in the sex lives of others!

[Paula · Rating 4 out of 5]

Educational and so useful (people should know more, even when they think they know quite a lot), but -- a lot of numbers. I know it's a statistics' book but sometimes it was just overwhelming. Oh, and the author had a quirky sense of humour :) Take your time and have a look, there are many very applicable chapters.

[James Miller · Rating 5 out of 5]

Statistics never felt so good. Very informative; very interesting and useful for some of my students studying sex-crimes at A-Level. Some graphs would have been better in colour, but presumably the price of the book would rise. Steamy stuff and at times jolly funny. The man himself was very good on the Infinite Monkey Cage talking about his work and its ins and outs.

[Gavin · Rating 4 out of 5]

Fun with a serious scientific mission. The expected titillating facts are present (how many people have tried anal? How many people are gay? What's typical?) but there's also an intro to the many difficulties of social science and a history of sexology in here. You learn why you should admire (but not trust) Ellis, Hirschfeld, Kinsey, Masters & Johnson, Hite...

Something for everyone.

[Raj Rajkumar · Rating 4 out of 5]

Does exactly what the title says. Interesting historical tidbits as well as median estimates for everything you wanted to know, but were afraid to ask!

[Jace · Rating 4 out of 5]

Sex by Numbers by David Spiegelhalter is an informative book about sex (largely focused in the UK and to some extent, the US) using statistical data

Thoughts while reading:
-It’s not surprising that it’s so hard to get data on people’s sexual practices considering how taboo the topic remains. The part about using fake lie detectors when surveying people was interesting
-It was fascinating to hear more about Kinsey’s research, and how his questions assumed people already did certain things.
-It’s not surprising that in the distant past, oral sex was more taboo, considering people’s hygiene practices. Really interesting to consider that common sexual positions were cultural though
-There’s a lot of taboo about masturbation in countries with a history of Christianity, so it makes me curious how it was in other countries (and some cultures seem to think that losing semen somehow causes a loss in life force)
-It’s interesting that women who regularly have sex masturbate more than those that don’t.
-I know that idea of men thinking of sex every seven seconds was disproven but it was nice to see actual data (and that they think of food about as often as they think of sex)
-Interesting to see that births declined even before there was the birth control pill. It was also interesting to see more solid data about fertility and age
-It was fascinating to see how dates of births change, and how people, even far back in time, did some degree of family planning to have children at more favourable times
-It was kind of funny that there was a period of time where an unmarried woman living with a man got labelled as a prostitute
-Interesting to learn about the factors that can influence the sex of a baby

Parts of the book were a bit dry but it was also informative. I would give it 3.5 out of 5

[Nadvornix · Rating 4 out of 5]

In a field where it is hard to find an accurate number, this book is a good overview of what do we actually know. At its the center are statistics done on representative samples of the population. So it talks about what the average person does and what the distribution of things like number of partners and first intercourse and so on. Not about extremes and oddities.
There is a strong emphasis on the quality of the statistics. With nice habit that many statistics have ratings with number of stars corresponding to their quality (In 1938 half of brides under 20 were pregnant is accurate with 4*. There are 25,000 trafficed prostituted in UK: 0*)
Spiegelhalter makes good use of every bit of Victorian-era statistics available. And he nicely shows interesting characters who collected them. And, thankfully, briefly, too, so that after a paragraph of biography it quickly gets back to the numbers, so that the book contains little of the standard biographical filler of pop books.
The boring factors are the (necessary) abundance of discussion of the methodology of the various statistics, and the focus on the average of the general population, rather than the extremes. What's fascinating is the understanding of how things really are.

Random facts:
- median frequency of sex per 4 weeks dropped between 1990 and 2010 from 5 to 3.
- median "intravaginal ejaculatory latency time" is 9 minutes (3*)
- From 1990 to 2010, the proportion of people for whom infidelity is "morally unacceptable" doubled. The only country in the dataset where less than 50% of people think so is France.
- 82% of adolescents in US pledging virginity before marriage later denied they made the pledge.
- in 1990 only 30% of women around 50 had given or received oral sex in the last year

[Merve · Rating 3 out of 5]

Bir sosyolog olarak istatistiki verileri takip etmek ve yorumlamak benim işim belki. Ancak istatistik en az ilgimi çeken alanlardan biriymiş bildiğim şey bu kitap elimde süründükçe daha kesin bir hal aldı. Cinsellik, bütün tabuları, ilgi ve cazibe halleriyle birlikte büyük bir yer kaplıyor yaşamımızda. En acısı da güç ve hiyerarşi ilişkilerini derinleştiren bir yanı da var tanımlanma biçimine bağlı olarak. İlgi çekici bir konu. İlgi çekecek bir kitap aslında sayısal verilerle analitik çözümlemeleri takip etmekten keyif alanlar için. Ben bu alanla ilgili daha sosyolojik, psikolojik analizlerin olduğu özellikle de toplumsal cinsiyet duyarlılığı taşıyan kitaplardan daha keyif alıyormuşum. Bu gerçeği bir kez daha anladım.

[Monika · Rating 5 out of 5]

Where else could I find out that people with higher education are more likely to have oral sex?

But in all seriousness, this book actually covers a lot about the quality of research methods, sampling bias and how much we should trust some data more than others and why. All of that but then all of the data is about sex so then it's like a 100% more memorable (0* data according to Spiegelhalter's system). The book also covers a lot of important topics such as the likelihood of pregnancy depending on age, which is vital as some of information out there wildly misrepresents the actual likelihood of getting pregnant in your 30s.

All in all, a very interesting book covering everything about sex that we could possibly have data for.

[Js100]

A fascinating overview, with some wry humour. He gives stats star ratings, with many headlines rating zero or one. There are a few graphs and tables, which may make it a bit heavy going,for some, I found them fascinating, though hard to see on a tablet.

[Sash · Rating 5 out of 5]

This was so interesting, I’ve learnt so much about collecting data and the issues surrounding certain methods with this book but it was also written in a really engaging way. Despite it being a bit out of date due to when it was written still a great read!

[Anselm Priest · Rating 5 out of 5]

Excellent book

It is all about the numbers and the numbers are truly fascinating. Not a book about sex, so don't think it will arouse you. It is however, a fabulous read.
Highly recommended.

[Travis · Rating 3 out of 5]

I gave up on this, numbers and stats are interesting but it didn't seem to be gripping enough to keep me.

[Ben · Rating 3 out of 5]

Some interesting statistics that are probably a little bit out of date by now. Can be a bit of a dry read (ironically).

[Embla KS · Rating 5 out of 5]

Educational, interesting, and unexpected facts about human behaviour

[robert · Rating 2 out of 5]

Way too many numbers! All the statistics came across as very dry. Definitely some interesting statistics and facts. More sex facts and less statistics would have definitely helped.

[Chelsea · Rating 3 out of 5]

Fun but repetitive after a while.