Monday, October 16, 2006

300 * 10^6

Tomorrow some baby, probably in the Southwest US, and with a better than even chance of being Hispanic, will become the United States' 300 millionth living person.

When I was born, 1955, my arrival brought the total to exactly 165 millionish. That's quite the growth curve, although like all wealthy countries, it has become much less positive. That comfort and fecundity are seemingly at odds is a secular phenomena.

Unlike other wealthy countries though, the growth curve is still positive; even excluding immigration it is not negative. Such robust growth is unique among rich countries. As America adds 100m people over the next four decades, Japan and the EU are expected to lose almost 15m.
American women today can expect to have an average of 2.1 children. That is the number needed to keep a population stable, so observers sometimes take it as a given and say that America's population growth is entirely due to immigration. This obscures the point: for every big advanced country besides America and Israel, the alternative to “replacement rate” fertility is a baby bust.

The fertility rate in the EU is 1.47—well below replacement. By 2010, deaths there are expected to start outnumbering births, so from that point immigration will account for more than all its growth. And that average hides countries that have seen an astonishing collapse in the willingness of their citizens to breed. The fertility rate in Italy and Spain is 1.28, which, without immigration, would cause the number of Spaniards and Italians to halve in 42 years.


Which raises the question: What makes the US, in comparison to the rest of West, so fertile?

Religion plays a role ... Americans are more devout than Europeans ... and their faith colours their worldview. Don Iloff, a spokesman for Lakewood Church, agrees. Faith begets hope, he says, and if you have hope for the future, you are more likely to want to bring children into the world.

Fine. But why are all those readers of the Left Behind series having any children at all?

While some are inclined to echo this self congratulation and simplistic demonization, perhaps the answer is a little more involved, and the evidence more persuasive:

[Population experts] at the University of North Carolina cite several other possible factors. Birth rates are lower in more patriarchal rich countries, such as Japan and Italy, than in places where the sexes are more equal, such as America and Scandinavia. Perhaps the knowledge that Dad will help with the housework makes women more willing to have children.

America's wide open spaces also make child-rearing more attractive. Bringing up a large family in a tiny Japanese apartment is a struggle, even if you can fold away your bed during the day. The world's lowest fertility rates are in super-crowded Hong Kong (0.95), Macau (1.02) and Singapore (1.06). In America the average family-home has doubled in size in the past half-century, from 1,000 square feet (93 square metres) in 1950 to 2,100 square feet in 2001.


Those experts might also have added that American's are probably paying a slightly smaller proportion of their after-tax income to buy that larger house, too.

If I were to become HDWIC, I'd keep the tax rates low, the government's intrusion into the economy light, and leave religion alone to take care of itself.

Seems to have worked pretty well so far.

23 Comments:

Blogger Bret said...

I did a bit of analysis of birth rates here and concluded that population density accounts for the majority of the variance in birth rates. I don't think either religion or patriarchy really play that large of a role.

October 16, 2006 2:25 PM  
Blogger Harry Eagar said...

If it's correct -- as used to be assumed -- that birth rates fell primarily for two or three reasons (declining value of adolescent labor; greater survival of children to adulthood; rising expense of raising children to compete in middle class adulthood), then presumably eliminating any of those three variables would tend to raise the birth rate, no matter the religious outlook.

Thus, keeping taxes low, as Skipper suggests, would alleviate the third problem. Making college almost no cost to parents in the '50s and early '60s was a brilliant stroke by the Americans; and washing out a lot of likely young people with the 11-Plus system was like to be fatal for the UK.

Finding a religious motive for large families is important to some people, but there's no very clear evidence that it counts, except in some minority sects like LDS.

I read a study of a Muslim village in Punjab years ago (cannot recall author), which linked declining family size almost entirely to rising income. There was no obvious change in religious outlook, despite the demographic switch.

It does seem to me that most of the rich people I come in contact with have large families.

October 16, 2006 3:35 PM  
Blogger Peter Burnet said...

It is certainly true that material prosperity has a dampening effect on the birthrate. The trouble with your conclusion that religion is of little influence is that prosperity also has a dampening effect on religious belief and observance. So, chicken or egg?

Bret, I believe you may have been a little selective with your test countries. If your general hypothesis were correct, the birthrates in India, Indonesia and Bangladesh would have fallen off generations ago and we Canadians would be breeding like rabbits.

This is the kind of argument we get into in the evolution posts. Bret, explain to me how general statistics on population densities translate into decisions at the individual couple level. "Sorry dear, I'd like another too, but the traffic outside is just too congested." No one I've ever met thinks that way, so is it all unconscious determinism? Is it local or national? I can sense vaguely (and irrationally) how living in a high-density city like Toronto might have some influence on average family planning, but then shouldn't the birthrate in rural Saskatchewan be much higher? And if it is not, is there some mystical way these folks unconsciously influenced by density are averaging it all out within national boundaries?

October 17, 2006 5:50 AM  
Blogger M Ali said...

I recall reading somewhere that the biggest factor in fertility declines in developing countries was female literacy.

In advanced industrial nations, affordable family formation - i.e. lots of cheap homes with yards - is key to keeping birthrates higher.

October 17, 2006 8:59 AM  
Blogger Harry Eagar said...

If you say prosperity dampens religious belief, then you have to explain why America, when it was by far the most prosperous of countries, remained pretty religious.

I think the link is not prosperity:religion but wider experience:religion.

The loss of faith doesn't kick in until long after prosperity comes in.

In the Punjabi example I referred to, the level of prosperity was relative. The people remained poor. But they began to dream of a motorbike or sending one son to the kind of school that could result in a government job.

Another obvious influence, perhaps subsumed under 'declining value of adolescent labor,' is migration from countryside to city.

October 17, 2006 10:52 AM  
Blogger Hey Skipper said...

Peter:

The trouble with your conclusion that religion is of little influence is that prosperity also has a dampening effect on religious belief and observance. So, chicken or egg?

Just to be clear, I'm not concluding religion is of little influence. Rather, I am concluding that an exclusive focus upon religion as being all important almost certainly excludes other factors that may, in fact, turn out to be significant.

I doubt religious belief can be excluded, but I'll bet it is one of a half dozen factors.

f your general hypothesis were correct, the birthrates in India, Indonesia and Bangladesh would have fallen off generations ago and we Canadians would be breeding like rabbits.

I think Bret is making an argument confined to a specific set of countries. That is, for those countries who have made the wealth (and, as Ali noted, the female literacy) driven demographic transition, those with lower population densities tend to have higher fertility rates.

Since the US and Canada are similar in many ways, it would be interesting to note the difference in fertility between the two. This article, while drawing no firm conclusions, points to the 0.3 child/woman difference between the two countries (US non-Hispanic 1.85; Canada 1.52) as being the result of economics, as well as other factors that could well be placed at religion's doorstep (earlier marriage, higher marriage rates in US).

It is worth noting that in the last generation, the Mormon birth rate has halved, from about 4.3 to 2.6, despite overt theological motivation to have large families. That is a substantial drop in a short time, which I doubt can be accounted for by changes in religious belief alone.

... explain to me how general statistics on population densities translate into decisions at the individual couple level.

Well, if housing costs are very high due to density, and the second child was a different sex than the first, the eventual requirement to go from a two bedroom flat to three might be prohibitive.

I'll bet one of the reasons US couples increasingly limit their families to two or fewer children is the very high cost of college education.

Europe has very high marginal tax rates, no, or little, ability to mitigate housing costs through increased supply, and stagnant economies due to over regulation.

All of those are more or less amenable to change; it seem likely that if those factors would become more like the US, the birth rate would respond accordingly.

Whether there would still be some remaining deficit due to lapsed religious belief is very difficult to say, which leads to my conclusion that reliance upon religion as the sole factor is, at the very least, simplistic.

October 17, 2006 12:00 PM  
Blogger Peter Burnet said...

Rather, I am concluding that an exclusive focus upon religion as being all important almost certainly excludes other factors that may, in fact, turn out to be significant..

Aha! I love you Duckians. When you are forced by evidence to link religion to something you rather like and are in favour of, you emphasize it's marginality and all the myriad other factors in play. Switch to something that you don't like and its 100% unadulterated blame, no?

October 17, 2006 3:58 PM  
Blogger Bret said...

Peter Burnet wrote: "I believe you may have been a little selective with your test countries. If your general hypothesis were correct, the birthrates in India, Indonesia and Bangladesh would have fallen off generations ago and we Canadians would be breeding like rabbits."

As stated in the post, I specifically picked "some of the more populated countries in the developed world". That would exclude India, Indonesia, and Bangladesh because they're not developed and Canada because it's not particularly populated. I'd also exclude Canada because much of it is frozen wasteland and not particularly inhabitable so calculating a population density that makes sense would be difficult.

Those are the ones I picked, then I did the analysis. I didn't pick others and then exclude them because they didn't fit the data. Thinking about it again, I would still pick the same set, maybe adding Britain which I'd guess fits in with the rest of the trend pretty well. The set includes the developed countries with large populations and are thus most comparable from a population density point of view.

I agree that prosperity is also a factor. I still rather doubt religion is a big factor.

Peter Burnet also wrote: "explain to me how general statistics on population densities translate into decisions at the individual couple level."

I take it you've never lived in a big city? It goes something like "sorry, dear, I'd like another but we don't have room and we can only afford a small, two bedroom apartment near where we both have to work to make ends meet or we can move to the 'burbs where I can commute two hours round trip every day so I won't be able to help much with parenting since I'll be busy commuting."

Again, other mammals adjust their fertility rate based on available resources. I think it's probably mostly innate in human behaviors. My understanding is that urban environments have always been population sinks, even in ancient times.

October 17, 2006 10:28 PM  
Blogger Harry Eagar said...

'something you rather like and are in favour of'

I have no particular opinion about what family size should be.

As an ex-Catholic, I find it amusing that people claim a religion that promotes lifetime abstinence and complains that not enough people take it up is credited with helping to expand the population.

Same for Tibetan Buddhism. Or are you going to argue that Buddhists are not religious?

October 17, 2006 10:34 PM  
Blogger Peter Burnet said...

I think we aren't probing deeply enough on this one. Whether one is prosperous, lives in a high density area or is formally religious or not may offer some interesting and inconclusive correlations, but the heart of the matter is the degree to which people consciously plan their lives and futures. If replacement rate without immigration is 2.1, then the average couple must "decide" to have three, which means a significant number must choose to have four or five. I doubt there are too many couples who express that conscious wish on their wedding day--too abstract and scary.

I've never bought into the theory that people used to have lots of kids to provide security in old age, although almost everyone seems to believe it. It is simply too economically irrational. I think the reason people had so many kids is they didn't think about it--it just came naturally. They didn't "want" eight kids in the sense that we mean, but they loved them nonetheless when they arrived. They didn't plan for their old age either. Firstly it was dicey whether they would ever see it and if they did it was likely to be short. The exception was the well-to-do, who were notorious for relative infecundity.

Today, when the prudent person consciously salts away several hundred thousand dollars to cover the cost of dying and we think that a wanted child is one that is or should be wanted before he is even conceived, there is all sorts of pressure against large families.

So, religion plays a role among the consciously fervent like the Amish or Orthodox Jews, but generally it's influence is tangenital. There is no reason to expect large families from simple churchgoing and belief in God, but it does make a difference whether you see life as something you plan and control or see it as something that largely happens to you. That is not unrelated to religion.

Bret:

I could write a whole book on the American propensity to describe Canada as a "frozen wasteland" to cover up statistical flaws in their theories, but I'll save it for another time. :-)

October 18, 2006 3:59 AM  
Blogger Hey Skipper said...

Peter:

. If replacement rate without immigration is 2.1, then the average couple must "decide" to have three, which means a significant number must choose to have four or five.

That is some way scary math, friend.

In order to get to 2.1, nine couples may choose two, while one couple chooses three. If one couple chooses four, and one three, then another couple may choose none, etc.

In other words, the median is 2, the distribution is very narrow around two, but is skewed very slightly to the right.

When you are forced by evidence to link religion to something you rather like and are in favour of, you emphasize it's marginality and all the myriad other factors in play. Switch to something that you don't like and its 100% unadulterated blame, no?

I'll go with 'No.'

Religion, for all its appeals to the supernatural, is strictly a material phenomena. As a materialist, I am interested in the impact religion has on life. In some respects, charitable works, say, religious belief is very important.

In this particular case, belief does seem to have an impact, but it is clearly not predominant. Any analysis that makes it so is either simplistic or self-congratulatory.

Where the material consequences of religion are pernicious, once the case for Christianity, and very much still the case for Islam, then religion deserves the blame, no?

October 18, 2006 7:54 AM  
Blogger Peter Burnet said...

Yes, you're right about the math. I double-counted the early death, emmigration etc. factor by forgetting that it is already written into the 2.1 figure.

Too bad you aren't nearly as good at understanding religion as you are math.

October 18, 2006 9:13 AM  
Blogger Bret said...

Actually, I'll agree with Peter on this math. To actually get 2.1 children on average, the average couple probably does need to decide to have close to three children because many couples can't have children at all, regardless of what they decide, other couples can't have as many as they decide even if they do squeak out one or two, and other couples divorce and end up with fewer than they expect. Perhaps that's not what Peter meant, but that's what I assumed.

My family first immigrated to Canada when coming from Eastern Europe and the bulk still lives in Toronto so I feel perfectly justified in identifying Canada as the frozen wasteland that it is. Though admittedly, now that I've lived in San Diego for over 20 years, anything north of LA is a frozen wasteland. After all, the only reason I ever go North of LA by choice is to ski.

October 18, 2006 9:38 PM  
Blogger Brit said...

I'm lost. How can you decide to have "close to three children"?

October 19, 2006 2:04 AM  
Blogger Peter Burnet said...

Brit:

The wife wants a third and the husband is whining and dissembling. In 80% of the cases, he gives in to keep the peace. Presto, a 2.8 birthrate.

October 19, 2006 5:16 AM  
Blogger Bret said...

Sorry, that should have been "decide to have close to three children on average".

October 19, 2006 6:01 AM  
Blogger Hey Skipper said...

Bret:

Sorry, that should have been "decide to have close to three children on average".

I ordinarily defer without question to your mathematical expertise, but not here. I think you have resorted to some dodgy double entry accounting: you have taken an average of 2.1, and turned it into an average of nearly three.

The 0.1 accounts for those women having fewer than 2, and for those female children who, for whatever reason, fail to have any children themselves.

So if your society consists of ten women, and they have twenty one children, then the population will remain stable into the next generation.

How those twenty one are doled out among the ten women has nothing whatsoever to do with the average lifetime fertility per woman.

October 19, 2006 10:26 AM  
Blogger Harry Eagar said...

I dunno about people not discussing children before marriage.

Tricia and I did, and all my kids did.

So far, except for the one who decided she didn't want any, none of us has come anywhere near the prenuptial target.

I would expect that most people explore this at least to the extent of 'Do you want a big family?'

October 19, 2006 1:32 PM  
Blogger Bret said...

Hey Skipper wrote: "The 0.1 accounts for those women having fewer than 2, and for those female children who, for whatever reason, fail to have any children themselves."

The 0.1 accounts only for the child mortality rate (in this case those that die before 15 years of age). From Wikipedia:

"Replacement fertility is the total fertility rate at which women would have only enough children to replace themselves and their partner. By definition, replacement is only considered to have occurred when the offspring reach 15 years of age. If all offspring survived to the age of 15 the replacement rate would be exactly 2, but in practice it is affected by childhood mortality. The replacement fertility rate is roughly 2.1 births per woman for most industrialized countries and has not been evaluated for poorer countries. At this rate, population growth through reproduction will be approximately zero, but will also be affected by male-female ratios and mortality rates."

Can you see that Wikipedia definition is different than what you wrote? Given the Wikipedia definition, can you see my analysis?

October 19, 2006 5:20 PM  
Blogger Brit said...

I don't understand how you can conclude from an average of 2.1 that most people plan to have 3.

Some people have more than they plan.

Doesn't an average of 2.1 just indicate that the average is 2.1?

October 20, 2006 1:26 AM  
Blogger Bret said...

Oy!

I'm not sure why we're all confused (or maybe just I'm confused) and it's not particularly important, but let me give it one last try.

All I'm trying to ay is that there is likely a discrepancy between the number of children people "decide" or "intend" or "plan" to have and how many they actually have.

For example, if a given woman at age 15 decides that she will try to have 10 children during her lifetime but only actually manages to have 4, there is a difference of 6 children between intended (decided) and actual. In general, for woman i, this might be written (given I can't do subscripts in comments):

Ca(i) = Ci(i) + delta(i)

Where Ca is the actual number of Children the woman has, Ci is the intended (decided) number of Children the woman wants, and delta is the difference.

Total fertility rate is a somewhat more complicated formula than an average, but let's just use averages for simplicity. For a population of N women, the average number of children per women is:

Ave(Ca) = Sum(i=1,N; Ca(i)) =
Sum(i=1,N; Ci(i) + delta(i) =
Ave(Ci) + Ave(delta)

In words, the average number of children actually born per woman is equal to the average number of children that each woman decides she wants plus the average discrepancy (delta) between the number of children each woman decides she wants and actually has.

There's no reason that Ave(delta) should be zero. My belief is that Ave(delta) is significantly negative. In other words, infertility problems and underfertility problems overwhelm overfertility issues. That happens to fit my personal obervations in that I know of a lot more people who wanted children and don't have them, than those who wanted fewer children than they have (though admittedly, the latter group may be far less vocal).

October 20, 2006 10:31 AM  
Blogger Hey Skipper said...

Bret:

Given the Wikipedia definition, can you see my analysis?

Well, no. Total lifetime fertility is per woman, not per couple. Clearly, in order for there to be an average TLF of 2.1 (or any number, for that matter), there have to be enough women above the average to balance those below.

But that alone is no reason to conclude To actually get 2.1 children on average, the average couple probably does need to decide to have close to three children because many couples can't have children at all, regardless of what they decide.

That might be the case, but in order to reach that end, either many women can't have children, due to physical factors, or an unwillingness to bear children out of wedlock, combined with a low marriage rate.

Clearly, for those women who have no children, or one child, then there will have to be corresponding women who have three or more.

But I suspect that if you were to plot the number of women against number of births in the range 0 through 10, the bars would be very high at 1 and 2, and fall off very rapidly beyond that.

As it turns out, that is the case. 28% of women, hardly "average" have three or more children, and 36% have zero or one.

This has me very confused:

In words, the average number of children actually born per woman is equal to the average number of children that each woman decides she wants plus the average discrepancy (delta) between the number of children each woman decides she wants and actually has.

Sorry, but it appears to me that the average number of children per woman is equal to the number of live births divided by the number of women, period.

October 20, 2006 12:32 PM  
Blogger Bret said...

Hey Skipper wrote: "...it appears to me that the average number of children per woman is equal to the number of live births divided by the number of women..."

Sure, I agree. I'm not arguing against that at all. The point I'm trying to make is about the relationship between live births and deciding how many children to have. It's a pretty unimportant point, so let's not worry about it.

October 20, 2006 5:50 PM  

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