Research at the University of Utah analysed the effect of men/women ratio on crime rates in 3,082 US counties using census and crime data from 2010. The study focused on men and women of reproductive age and five types of crime: murders, assaults, rapes, sex-offences and prostitution.
"For all types of offence analysed, rising proportions of men correlated with fewer crimes - even when accounting for other potential contributing factors such as poverty."
It seems that when there are fewer women, men see them as a more valuable resource - and their behaviour becomes more 'dutiful' to win and keep a female partner. When there are many women, men adopt promiscuous behaviour, which in turn brings them into conflict with other men.
Animal studies show similar patterns. "When females are abundant and males rare, males are more violently competitive, more promiscuous and less likely to invest in offspring."
Studies at the Univestity of Texas show that when women outnumber men, there are more short-term relationships, higher divorce rates and increased reluctance to commit to one partner.
These studies have implications for crime prevention. Current policies aimed at reducing violence and crime by reducing the proportion of men in male-dominated areas may backfire.
Source: Men get violent if women are aplenty by Andy Coghlan in New Scientist, 8 Oct. 2016
