Monday, January 12, 2009

More Demographic Trivia

I was reading an article the other day in which an self-titled "mother" of the Pill, Carl Djerassi, bemoaned the demographic crisis gripping Europe (and his home country of Austria in particular). One particular sentence stood out to me. Cardinal Schonborn of Austria said, commenting on Dr. Djerassi's statements, ""Somebody above suspicion like Carl Djerassi ... is saying that each family has to produce three children to maintain population levels, but we're far away from that," he said."

Now, my first reaction when reading a statement like that is bullshit. The average woman needs to have ~2.1 children (assuming typical infant mortality, etc.) for a population to achieve zero growth/decline in the long run. However, Mr. Schonborn didn't relate the population stability to the typical statistic. He referenced it to the the number of children within given families. That's really an entirely different statistic, with a whole host of subtle factors affecting it.

1) The marriage rate
2) The rate of illegitimate births
3) Sex ratios
on top of the usual factors
4) average age of first childbirth
5) mean pregnancy intervals
6) infant mortality
7) mortality rate of child bearing aged women
8) I'm sure there are more that I'm missing...

All of these factors mean that the average woman who ends up having children, needs to have even more than 2.1 in order for the population to remain stable. However, what is the number? Could it possibly reach even 2.5 (for which one might forgive Mr. Schonborn for rounding up to three)? Personally, I'm skeptical, but I suppose it's not outside the realm of possibility, especially in developed countries where more and more women choose not to have any kids whatsoever, leaving a large tail on the bell curve. Actually, come to think of it, it would probably be more like an F- distribution than a Gaussian distribution, but I digress.

If anybody knows what this number should be, I'd appreciate them passing it along. I couldn't find it, and I find the question intrigueing: how many children does the average woman who has any children need to have to maintain stable population levels.

Getting to the crux of Dr. Djerassi's concern, Austria has been below replacement level fertility since the early 1970's (Table A.15), and is currently experiencing a net reproduction rate of 0.66. That number astounds me. It basically means the potential (barring immigration) for a society to replenish its population falls by 1/3 in each generation. One third decrease in population per generation if the rate remains unchanged... Incredible. It basically spells the death-nell for the nanny state in Austria, barring some radical changes to birth or immigration rates. Luckily for Austria (and the US), it takes decades for fallen birthrates to trash the economy and have a significant effect on the ability of the government to provide benefits for the retired. Unfortunately, it's a much harder nut to crack. Once a significant proportion of the young realize that they can live the high life without kids, marketing companies get in there do their best to perpetuate/grow that lucrative market. It's tough to convince the next generation that what they really need to do is sacrifice and have more kids to pay for the retirement benefits of past generations that lived it up, when there are marketing companies working night and day to convey exactly the opposite message.

MB

Update: This article says that nearly 20% of women aged 40-44 are childless in the US. I ran across another article that put the childless rate of all German women at 30% (40% for college grads). Given that our birthrate is light years ahead of Austria's, there might be something to Schonborn's statement. I found this article about Austria in particular, detailing the changing birthrate levels and distributions, but honestly, it's too detailed and I'm too tired to understand it. http://www.demogr.mpg.de/papers/working/wp-2004-028.pdf

g'night.

3 comments:

Anonymous said...

This is a fascinating subject to me, because I'm old enough to remember Paul Ehrlich's "Population Bomb" scare of the 1970s. Ehrlich was an entomologist who studied butterflies, but his panic-mongering book was completely embraced by the Left. (Basically, he was the Al Gore of his day). You wouldn't believe the slanderous comments I got when people found out I was from a large family. To show how the Left protects their own, Ehrlich is still an honored professor at Stanford. Meanwhile, the population bomb is real, but it's 180 degrees opposite of his prediction. I highly recommend the book "America Alone" by Mark Steyn. We are "alone" among western democracies because our population is maintaining a holding pattern (birthrate of 2.1). The numbers for Greece, Italy, Spain, Taiwan, Japan.... well, all our allies, are mind-boggling. China and Russia are also committing slow suicide. Japan for example is just barely above 1 child per woman. Every twenty years, there are half the potential mommies. That's a geometric crash, and Japan is an ethnically homogenous country, unable (so far) to import a third world work force. I forget Mark Steyn's numbers, but if you follow the geometric progression, it's something like: in 300 years the total population of Japan can fit in a school gymnasium. Naturally, some cataclysm will happen to Japan before then. Israel also is hearing the bell toll. They are desperately trying to import Jews to make up for the less-than-replacement fertility of their people, while they are surrounded by Palestinians and Arabs with mind-boggling fertility rates of between 7 and 9 children per woman. At some point either Israel as a country loses its Jewish character, or it sets up an apartheid system to take away the vote from those Arabs within its borders who would be happy to take over the Knesset and wipe out Jewish influence. The Bible says a lot about the importance and blessing of children, but modern Israel, like every country of western Europe (save maybe Ireland), is an overwhelmingly secular society. Secularism embraces death (abortion and euthanasia, the tools of me-centered Humanism), thus providing the ultimate irony that Secularism proves itself unfit to carry forward Darwinism.
--Brad

MarkC said...

Welcome, Brad! It's great to have you joining the discussion.

Secularism is unfit to carry forward Darwinism... that is ironic indeed!

Mark

MamasBoy said...

Now that I've had a bit of time to think about it, it seems like a rather easy problem to figure out how many kids the average non-childless woman must have to replace the population. Just divide the number of children statistically necessary to replace population by the percentage of women who have kids.

For Austria, the childless rate is 23.2% for the female 1965 birth cohort, leaving 76.8% of their female counterparts to do all the child rearing. Assuming 2.1 kids is necessary to replace the population, then the average child bearing woman needs to have 2.73 kids on average. Given the US's childless rate of 19% according the an article in American Demographics (http://findarticles.com/p/articles/mi_m4021/is_2001_Oct_1/ai_79052844), the average child bearing American woman must have 2.6 kids to replace the population (ignoring immigration).

That's kind of weird to think about. I work for a small engineering firm (~50 people) with lots of childless couples. My wife is about to have our third, making me only the third person that I know of in the company to surpass the 2 mark. I feel like a bit of an alien, actually wanting more than 2 kids in my company, when there are more childless employees than employees with kids. It's an interesting twist to think that an odd duck like me is merely keeping up with the basic replacement pattern for society when rounding is considered.

MB