Intense financial pressure on Chinese men to attract a partner and the behavioural effects of growing up in a male-heavy environment are making them more likely to engage in criminal activities. That is the central finding of research by Lisa Cameron, Xin Meng and Dandan Zhang, which is forthcoming in the Economic Journal.

Their study notes that China’s ‘one child policy’ – in conjunction with Chinese parents’ strong preference for sons and sex selection aided by the use of pre-natal ultrasound – has led to there being approximately 120 boys for every 100 girls surviving infancy in China. At the same time, as more males have been produced, crime has been skyrocketing: a more than six-fold rise in crime rates over the past three decades.

The researchers explore whether these trends are related or feeding into one another. China’s skewed sex ratio has resulted in 30 million more men than women and tremendous difficulty for men in finding a wife. It also means that boys are growing up in an environment surrounded by many more boys than girls.

The study collects data from male inmates of a Chinese prison and similar non-inmates, and shows that the skewed sex ratio accounts for a 34% increase in China’s rate of incarceration.

This increase in crime is mainly due to the financial pressures that men face in attracting a wife. Men are finding it difficult, and in many cases impossible, to find a wife and brides are becoming increasingly expensive. It is not unusual for families to expect the bridegroom to supply an apartment and a substantial cash gift, often amounting to more than ten thousand pounds.

This turns some unmarried men to financially rewarding crimes. A high ratio of men to women in a man’s marriage market (defined in relation to his age and geographical origin) is shown to be associated with higher rates of financial crimes, not physically violent crimes.

A further (smaller) portion of the increase in crime is due to an increased willingness to take risks and increased neuroticism among men who grew up in heavily male environments. Behaviour in experimental games and responses to survey questions show that men who grew up surrounded by more boys than girls are more impatient, risk-loving and neurotic.

Risk-taking and neuroticism are strongly associated with the probability of engaging in criminal activity and being incarcerated. A ten percentage point increase in the sex ratio in the cohort in which a man grew up (for example, from the naturally occurring sex ratio of 1.07 to 1.17) is associated with a 5% increase in the probability of being incarcerated via behavioural channels.

China recently relaxed the one child policy to allow all couples to have two children. Some researchers have predicted little change in fertility behaviour as the Chinese have become accustomed to single children and the financial and other competitive pressures of life limit the ability of parents to feel they can support more children.

Even if the policy does result in a swing back to more girls, it will take at least a generation for the ratio between men and women of marriageable age to approach parity. The current marriage market pressures are likely to be sustained and possibly worsen in the short term, with the concomitant incentives to engage in crime.

China’s Sex Ratio and Crime: Behavioural Change or Financial Necessity?’ by Lisa Cameron, Xin Meng and Dandan Zhang is forthcoming in the Economic Journal.