Gender ratios in US - number of men declining

Human biology has always ensured that male births outnumber female ones by about 5%. It’s been long expected that for every 100 girls born, there will be about 105 boys. This balances out the higher death rate among male fetuses and infants.
A recent study done by Dr. Devra Lee Davis, a professor of epidemiology (at the University of Pittsburgh Graduate School of Public Health) has found the proportion of boys in US dropped from 105.5 per 100 girls in 1970 to 104.6 in 2001. The changes over last 30 years may seem small, but the researchers suspect they are one manifestation of paternal exposure to environmental toxins, such as certain pesticides, heavy metals, solvents or dioxins.
According to 2005 World Health Organization figures (see below), there are 73.4 million more men than women in China and India; but in US, women outnumber men by 5 millions, which could be the accumulative result of gender ratios imbalance at birth.
Gender Ratios


Biby Cletus said...

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Warm Regards

Biby Cletus - Blog

Bilbo said...

This is a very interesting statistic. The extraordinarily large surplus of men relative to women in China may be a reflection in part of the government's one-child rule and the traditional preference for male children that leads to female infanticide. Overall, this is a fascinating topic: one wonders how nature knows to regulate the percentage of male and female children to maintain the correct balance, and why the number of males would be declining when the number of females does not. Great post! Thanks for giving us things to think about!

Annette said...

Love your blog. This entry makes me think of Jurasic Park. Nature finds a way.