Sex Ratio

Sex Ratio Represents the Number of Males to Females in a Population

Newborn babies lie on a bed before massage at Xining Children Hospital in Qinghai Province, China. Getty Images

Sex ratio is the demographic concept that measures the proportion of males to females in a given population. It is usually measured as the number of males per 100 females. The ratio is expressed as in the form of 105:100, where in this example there would be 105 males for every 100 females in a population.

Sex Ratio at Birth

The average natural sex ratio for humans from birth is approximately 105:100.

Scientists are not sure why there are 105 males born for every 100 females around the world. Some suggestions for this discrepancy are given as:

It is possible that over time, nature has compensated for males lost in war and other dangerous activities to better balance the sexes.

A more sexually active gender is more likely to produce offspring of their own gender. Thus, in a polygamous society (polygamy where one man has multiple wives), he is likely to have a greater proportion of offspring that are male.

It is possible that female infants are under-reported and not registered with the government as often as male babies.

Scientists also say that a woman with a slightly over average amount of testosterone is more likely to conceive a male.

Female infanticide or the abandonment, neglect, or malnutrition of female infants in cultures where males are favored may occur.

Today, sex-selective abortions are unfortunately common in countries like India and China.

The introduction of ultrasound machines throughout China in the 1990s led to a sex ratio of up to 120:100 at birth due to familial and cultural pressure to have one's only child as a male. Shortly after these facts became known, it became illegal for expectant couples to know the gender of their fetus.

Now, the sex ratio at birth in China has been reduced to 111:100.

The world's current sex ratio is somewhat on the high side – 107:100.

Extreme Sex Ratios

The countries that have the highest proportion of males to females are...

Armenia – 115:100
Azerbaijan – 114:100
Georgia – 113:100
India – 112:100
China – 111:100
Albania – 110:100

The United Kingdom and United States have a sex ratio of 105:100 while Canada has a sex ratio of 106:100.

The countries with the lowest proportion of males to females are...

Grenada and Liechtenstein – 100:100
Malawi and Barbados – 101:100

Adult Sex Ratio

The sex ratio among adults (ages 15-64) can be highly variable and is based on migration and death rates (especially due to war). Into late adulthood and old age, the sex ratio is often highly skewed toward females.

Some countries with very high proportions of males to females include...

United Arab Emirates – 274:100
Qatar – 218:100
Kuwait – 178:100
Oman – 140:100
Bahrain – 136:100
Saudi Arabia – 130:100

These oil-rich countries import many men to work and thus the ratio of males to females is highly disproportionate.

On the other hand, quite a few countries have far more females than males...

Chad - 84:100
Armenia – 88:100
El Salvador, Estonia, and Macau – 91:100
Lebanon – 92:100

Senior Sex Ratios

In later life, the life expectancy of men tends to be shorter than women and thus men die earlier in life. Thus, many countries have a very high proportion of women to men in the over age 65 range...

Russia – 45:100
Seychelles – 46:100
Belarus – 48:100
Latvia – 49:100

On the other extreme, Qatar has a +65 sex ratio of 292 men to 100 women. That is the most extreme sex ratio currently experienced. There are nearly three old men for every old woman. Maybe countries should begin to trade an over-abundance of elderly of one gender?