Human Sex Ratio - Gender Imbalance

Gender imbalance is a disparity between male and females in a population. As stated above, males usually exceed females at birth but subsequently experience different mortality rates due to many possible causes such as differential natural death rates, war casualties, and deliberate gender control.

According to Nicholas Kristof and Sheryl WuDunn, two Pulitzer Prize-winning reporters for the New York Times, violence against women is causing gender imbalances in many developing countries. These authors report that more girls have been killed in the last 50 years, just because they were girls, than the number of males who were killed in all the wars of the 20th century. They detail sex-selective infanticide in the developing world, particularly in China, India and Pakistan.

Commonly, countries with gender imbalances have three characteristics in common. The first is a rapid decline in fertility, either because of preference for smaller families or to comply with their nation's population control measures. Second, there's pressure for women to give birth to sons, often because of cultural preferences for male heirs. Third, families have widespread access to technology to selectively abort female fetuses.

As a contributing measure to gender imbalance in developing countries, Kristof and WuDunn's best estimate is that a girl in India, from 1 to 5 years of age, dies from discrimination every four minutes (132,000 deaths per year); that 39,000 girls in China die annually, within the first year of life, because parents didn’t give girls the same medical care and attention that boys received. The authors describe similar gender discrimination and gendercide in Congo, Kenya, Pakistan, Iraq, Bahrain, Thailand and many other developing countries.

Some of the factors suggested as causes of the gender imbalance are warfare (excess of females, notably in the wake of WWI in western Europe, and WWII, particularly in the Soviet Union); sex-selective abortion and infanticide (excess of males, notably in China as a result of the one-child policy, or in India); and large-scale migration, such as that by male labourers unable to bring their families with them (as in Qatar and other Gulf countries). Gender imbalance may result in the threat of social unrest, especially in the case of an excess of low-status young males unable to find spouses, and being recruited into the service of militaristic political factions. Economic factors such as male-majority industries and activities like the petrochemical, agriculture, engineering, military, and technology also have created a male gender imbalance in some areas dependent on one of these industries. Conversely, the entertainment, banking, tourism, fashion, and service industries may have resulted in a female-majority gender imbalance in some areas dependent on them.

One study found that the male-to-female sex ratio in the German state of Bavaria fell as low as 0.60 after the end of World War II for the most severely affected age cohort (those between 21 and 23 years old in 1946). This same study found that out-of-wedlock births spiked from approximately 10–15% during the inter-war years up to 22% at the end of the war. This increase in out-of-wedlock births was attributed to a change in the marriage market caused by the decline in the sex ratio.

The Northern Mariana Islands have the highest female ratio with 0.77 males per female. Qatar has the highest male ratio, with 2.87 males/female. For the group aged below 15, Sierra Leone has the highest female ratio with 0.96 males/female, and the Republic of Georgia and the People's Republic of China are tied for the highest male ratio with 1.13 males/female (according to the 2006 CIA World Factbook).

The value for the entire world population is 1.01 males/female, with 1.07 at birth, 1.06 for those under 15, 1.02 for those between 15 and 64, and 0.78 for those over 65.

The "First World" G7 members all have a gender ratio in the range of 0.95–0.98 for the total population, of 1.05–1.07 at birth, of 1.05–1.06 for the group below 15, of 1.00–1.04 for the group aged 15–64, and of 0.70–0.75 for those over 65.

Countries on the Arabian peninsula tend to have a 'natural' ratio of about 1.05 at birth but a very high ratio of males for those over 65 (Saudi Arabia 1.13, Arab Emirates 2.73, Qatar 2.84), indicating either an above-average mortality rate for females or a below-average mortality for males, or, more likely in this case, a large population of aging male guest workers. Conversely, countries of Eastern Europe (the Baltic states, Belarus, Ukraine, Russia) tend to have a 'normal' ratio at birth but a very low ratio of males among those over 65 (Russia 0.46, Latvia 0.48, Ukraine 0.52); similarly, Armenia has a far above average male ratio at birth (1.17), and a below-average male ratio above 65 (0.67). This effect may be caused by emigration and higher male mortality as result of higher Soviet era deaths; it may also be related to the enormous (by western standards) rate of alcoholism in the former Soviet states. Another possible contributory factor is an aging population, with a higher than normal proportion of relatively elderly people: we recall that due to higher differential mortality rates the ratio of males to females reduces for each year of age.

Sex ratio imbalances have many consequences. High ratios of males make it easier for women to marry, but harder for men. Analyses of how sex ratio imbalances affect personal consumption and intra-household distribution were pioneered by Gary Becker, Shoshana Grossbard-Shechtman, and Marcia Guttentag and Paul Secord. High ratios of males have a positive effect on marital fertility and women's share of household consumption and negative effects on non-marital cohabitation and fertility and women's labor supply. It has been shown that variation in sex ratio over time is inversely related to married women's labor supply in the U.S.