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Posts Tagged ‘demography’

Missing girls

Crossing the Nile to go to school - But how many girls live to go to school in Africa?

Last year I read a fascinating book, Unnatural Selection: Choosing Boys Over Girls, and the Consequences of a World Full of Men, by Mara Hvistendahl. She talks about the issue of missing women, how demographically, there should be more women than there are in many different countries of the world. The issue was the subject of an Economist cover nearly two years ago.

Tyler Cowen has alerted me to a fascinating paper on the subject, soberly entitled, Missing women: age and disease, by Siwan Anderson and Debraj Ray.

The authors, instead of doing a fairly high level comparison of ratios between men and women at birth, and men and women in the population as a whole, look at projections of the relative proportions of men and women given the same relative birth and death ratios between genders that happen in the first world. They readily point out that there are many different ways to work out what the “appropriate” relative birth and death rates are, but nevertheless they come up with some fascinating conclusions.

Our study of excess female deaths by age yields two key findings. First, once we control for natural variations in the sex ratio at birth, sub-Saharan Africa has as many missing women as India and China: significantly more as a percentage of the female population. Second, the majority of missing women are of adult age. Sub-Saharan Africa has no missing females at birth, while the corresponding proportion for India is under 11%. China’s missing females, in contrast, are largely prenatal. About 37–45% of them may be classified as missing at birth. But all these regions display missing women at a variety of ages. For instance, excess female mortality up to age 15 does not account for more than a third of the total in India or sub-Saharan Africa.

So the fascinating thing about this study for me is the complexity it adds to the story. While the standard story of why there are “missing women” is sex specific abortion and female infanticide, that is only really the explanation in China. In other countries, the story is much more complex, with relative female death rates much higher than males at a variety of ages, and in sub-Saharan Africa, particularly because of maternal death rates and deaths from HIV-AIDS.

Ultimately, the conclusion of the paper is not that different from the Economist’s attention grabbing “100 million missing women”. But the reasons are far more interesting.

We find approximately 20 million missing women in India, 58 million missing women in China, and 8 million missing women in sub-Saharan Africa. Look at the enormous difference between China and the other two regions (in flows all three regions were about the same). This comes from the fact that excess female deaths in China are clustered at age 0. We reiterate, though, that these estimates must be treated with a great deal of caution.

The missing women in India and sub-Saharan Africa are largely because a variety of causes (injury, suicide, various diseases) disproportionately kill the women there.  That’s a reason to worry, and potentially an easier issue to fix, if the will and the resources are available.

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Cross posted at my new blog actuarial eye.

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Fertility update

Last month, the annual fertility rates were released by the ABS. I last did a post on this two years ago, so it is time for an update.

My broad conclusion was that fertility rates are pretty stable in Australia, with the very important caveat that that stability is in the number of children the average woman has in her lifetime, not necessarily how old she is when she has them.

So first, the headline. In the last two years, the total fertility rate for Australia (which represents the average number of babies that a woman could expect to bear during her reproductive lifetime, assuming current age-specific fertility rates apply) has dropped from 1.97 in 2008 to 1.89 in 2010. That is a reasonably significant drop (nearly 0.1 of a child!).

But the movement in the headline fertility rate is always much more than the movement in the average fertility for a woman over her lifetime. Below, you can see that the lifetime fertility rate for women this century has stayed quite stable.

Source: ABS, my own analysis

Women born in 1933 had the most children, on average – 3.1 in total. But women born in 1966 (the most recent date for whom lifetime projection is reasonable) are expected to have 2.05 babies, on average, over their life.

So why does the headline rate move around so much? It is all to do with when women have their babies. Those women born in 1933 had already had two of their children by the age of 28.  In another three years, on average, they’d had another half a child. In contrast, the woman born in 1966 had had one child by the time she got to 28. And it took her until the age of 33 to have the next half a child (on average). But she was still having children in her late 30s and 40s – she was having 50% more children then than her mother’s generation 30 years earlier.

This graph shows that effect.

Source: ABS and my own analysis

Interestingly, the generation from 1906 shown in this graph is much more similar to that woman born in 1966. While the woman born in 1906 had more children in her twenties than her granddaughter’s generation, she kept having them well into her late 30s and 40s, even more than women who are that age now.

Every year the news of the latest statistics gives rise to articles like this one, pointing out that Australia is in danger of not reproducing its population. But while we do seem to be dropping under replacement rate slightly, the bigger news is the change in the age of most parents – that’s the main message from this year’s statistics.

Cross posted at my new blog actuarial eye.

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