Sex By Numbers is a lively and entertaining guide to the statistics of sex. Written by David Speigelhalter, Professor of Risk at Cambridge University, the book teaches statistical rigour through the ever sensational subject of sex.
Sex By Numbers Summary
Sex By Numbers is a fascinating statistical insight into human sexual behaviour.
Well researched, with a rigourous and entertaining style, the book covers topics including sexual frequency, sexual preferences, sexuality, partner count, prostitution, pregnancy, STIs and sexual impulses looking at the statistical information available and the limits of obtaining valid and accurate data.
Below are some of the key insights from the book.
- Obtaining accurate data on sexual behaviour, sexuality and other taboo topics presents huge problems for researchers.
- The media will always sensationalise statistical research on sex to suit their own purpose of selling human interest.
- Comparing sexual frequency with conceptions approximately 1 in 1000 sexual sessions results in a baby.
- Statistical analysis suggests that people consciously and subconsciously alter their sexual partner count and overrepresent towards round numbers.
- Our best guess for paternal discrepancy is 1 in 30 children.
- Typically 42% of UK marriages end in divorce with risk building towards year 7 (3%) and falling each year thereafter.
- The Kinsey survey is commendable for breaking taboos but overestimates sexual variety due to the research methods used (sample bias)
- Our best guess is that 1.7% identify as Gay/Lesbian, 1.8% as Bisexual and 0.3% as Transgender but reported behaviours of activities add to these percentages.
- Historical parish records for marriages vs. christenings suggests that approximately 20% of brides were pregnant when married in the 1800s.
- The rate of ‘Illegitimate’ (non-wedlock) children has risen from <10% towards 50% with accelerated growth from 1970s onwards.
- 45% of pregnancies are either ‘unplanned’ or ‘ambivalent’ based on the London assessment criteria in the UK.
- Prostitution in the UK is worth £5.3bn to the UK economy but accurate data is extremely difficult to obtain.
- In natural circumstances for every 20 women born, 21 men are born and this is most likely influenced by the frequency of sex taking place as male frequency spikes in the days following ovulation.