SEX RATIOS, SEXUAL INFIDELITY AND SEXUALLY TRANSMITTED INFECTIONS: New UK evidence

15 Apr 2019

Women outnumber men in the UK and this relative male scarcity increases sexual infidelity and sexually transmitted diseases. That is the main finding of research by Yifan Kang and Roland Pongou, to be presented at the Royal Economic Society's annual conference at the University of Warwick in April 2019.

 

Analysing data from the 2010-12 British National Survey of Sexual Attitudes and Lifestyles on a wide range of sexual behaviours and sexually transmitted infections (STIs), their study finds that reducing male scarcity would induce safer sexual behaviour and reduce the spread of sexual diseases. It would also curtail STIs in women more than in men.

 

In the 2010-12 British National Survey of Sexual Attitudes and Lifestyles, 166 out of every 1,000 women and 123 out of every 1,000 men reported having been diagnosed with an STI in their lifetime. Yet fewer women (146 out of every 1,000) than men (238 out of every 1,000) were found to have been unfaithful to their sexual partner during the previous five years.

 

In general, in societies like the UK where women outnumber men, heterosexual women are disproportionately affected by STIs, despite being less likely than their partner to be unfaithful. This raises an important question about the role of sex ratios in the spread of STIs.

 

The new study (Kang and Pongou, 2019) addresses this question using UK data. It finds that moving from a situation where the proportion of men is very low to the complete elimination of the population gender gap would reduce sexual infidelity by 19% and STI prevalence by 9%. Reducing male scarcity would curtail STIs in women more than in men.

 

The researchers first extend a model of (in)fidelity networks proposed by Pongou and Serrano (2013) to study sexual partnership formation among individuals who enjoy having multiple partners but do not want their partners to do likewise.

 

From this extension, they derive clear theoretical implications of how a reduction in male scarcity would affect sexual behaviour. Under assumptions about the prevalent gender norms in Western societies, they find that reducing male scarcity would induce more egalitarian sexual networks, leading to less infidelity in men and a greater reduction of STIs in women.

 

They test these predictions on data from the 2010-12 British National Survey of Sexual Attitudes and Lifestyles, combined with census data from 2001 and 2011.

 

They analyse a wide range of sexual behaviours, such as the total number of sexual partners during the last five years; the number of serial partners; the occurrence of overlapping relationships and concurrent relationships; and the practice of unprotected sex.

 

They also analyse a wide range of STIs, including chlamydia, gonorrhoea, warts and herpes. Their finding that reducing male scarcity would induce safer sexual behaviour and reduce the spread of sexual diseases is consistent across these outcomes.

 

The new study is the first to examine a wide range of sexual behaviours and STIs in a context in which these diseases represent an important public health concern. According to data from Public Health England, every year since 2008 the number of new STI cases in the UK has exceeded 415,000.

 

If the current rates of infection continue, total treatment costs will reach £363 million between 2015 and 2020 (Lucas, 2015). In addition, STIs impose a significant burden on the health of the infected individuals and their economic productivity. In the UK, these diseases are also more prevalent among heterosexual women, thus raising an issue of gender equity.

 

The new study implies that part of the solution to the threat posed by STIs lies in addressing the issue of male scarcity. At birth, males outnumber females, but this surplus turns into a deficit at older ages, owing to higher male mortality.

 

In the UK, even though the male-to-female ratio has been increasing over time (934 men for every 1,000 women in 1960 versus 976 men for every 1,000 women in 2017), there are still more women than men.

 

Excess male mortality is explained by both preconception and biological factors (Pongou, 2013). But recent research shows that in the context of developing countries, these factors can be constrained by better institutions (Pongou et al, 2017; Mabeu and Pongou, 2019). These findings invite more research on how excess male mortality can be eliminated in developed societies like the UK.

 

References

 

Kang, Y, and R Pongou (2019) ‘Sex Ratios, Sexual Infidelity, and STIs: Evidence from the United Kingdom’.

 

Lucas, S (2015) ‘Unprotected nation: An update on the financial and economic impacts of restricted contraceptive and sexual health services’.

 

Mabeu, M, and R Pongou (2019) ‘Democracy, Genes, and the Male Survival Disadvantage’, working paper.

 

Pongou, R, and R Serrano (2013) ‘Fidelity networks and long-run trends in HIV/AIDS gender gaps’, American Economic Review 103(3): 298-302.

 

Pongou, R, B Kuate Defo and Z Tsala Dimbuene (2017) ‘Excess male infant mortality: The gene-institution interactions’, American Economic Review 107(5): 541-45.

 

Yifan Kang

Department of Economics | University of Ottawa | +1 (343)-777-8179 | ykang027@uottawa.ca

Roland Pongou

Department of Economics | University of Ottawa | +1 (617)-586-9014 | rpongou@uottawa.ca