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August 17, 2003


As I’ve mentioned in previous posts, in many developed countries the level of reproduction, as measured by the Total Fertility Rate, is currently below the replacement rate (the level necessary to sustain the population). With current levels of infant mortality, the replacement rate is only about 2.1, but the TFR in many countries is below this. For example:

(Estimates for 2002, source ‘The World Fact Book’)

With the exception of the USA the TFRs are all below the replacement rate. American readers may take national pride in their greater fertility, but they should note that the TFR for non-Hispanic whites is below the replacement rate, and it is only the high rate among Hispanics that pulls up the US average.

If these TFRs continue indefinitely, then in the absence of net immigration total population would eventually fall. This point has not yet been reached (except perhaps in Italy), because in most developed countries there is significant net immigration, and life expectancy is also still rising. In the UK, for example, population is expected to grow from its present 60 million to 65 million by 2050.

A declining population is not necessarily a bad thing. A rising population may be good for economic growth, but not for the quality of life. A lot depends on the density of population. The prospect of a declining population will be more attractive in Japan, with 336 people per square km., or the UK, with 244, than in the USA, with only 29.

However, my main concern in this post is whether we can expect the current low fertility rates to continue.

First, as I’ve mentioned previously, the TFR is an artificial construct which mixes up the current fertility of different cohorts of women. If there is a trend for women to postpone childbearing until later in their reproductive lifespan, then there will be a time-lag during which the TFR will systematically understate eventual cohort fertility. In the UK, surveys of women show that they intend on average to have around 2 children, though the current TFR is only 1.7. Longitudinal studies show that women on average get close to their intended family size, though many women who postpone childbearing find it more difficult to conceive than they had expected, as fertility declines from age 30 onwards. I would guess that over the next decade the TFR will increase somewhat from the current low levels, but not quite to the replacement rate.

Over the longer term, can we expect the TFR to return to the replacement rate or even higher? Now that reliable contraception is available, the fertility of women depends largely on how many children they and their partners want. Assuming that the biological impulse to reproduce is constant, the demand for children will depend on the other costs and benefits of having them. Demographers and economists have analysed these non-biological factors. In developed countries the economic motive of having children to put them to work, or to support their parents in old age, is no longer relevant. The economic factors are therefore largely costs rather than benefits, such as the costs of food, housing, education, health, and child-care, and the opportunity cost for women of not working during pregnancy and after childbirth. In most countries the costs are to some extent spread over the whole community through taxes (e.g. to pay for education), but there is probably no developed country where it is economically advantageous to have children.

It is unlikely that the costs of children will fall greatly. A reduction in population might reduce the cost of housing, which is a major burden for young families in some countries, but this is a very long term prospect. It is also possible that governments will provide financial incentives for having children, but such policies have not proved effective in the past (notably in France), and in any event resources will be stretched to provide for the increasing number of the elderly.

Purely on economic grounds it is therefore difficult to foresee any major increase in fertility. But all of this assumes that the underlying impulse to have children is constant. This is doubtful. From a biological point of view, fertility is subject to natural selection. We expect average fertility to rise until it reaches an optimum, where the number of offspring in a family who themselve survive and reproduce is at its maximum. If a family has more offspring than the optimum, then the higher number of children will be more than offset by their lower rates of survival and/or reproduction - the parents will have more children but fewer grandchildren than the average.

The optimum fertility for a species depends on its ecological conditions and way of life. There is a familiar distinction between r-selected species, where a large number of offspring are produced, but most of them die, and k-selected species, where a small number of offspring are produced, but a high parental investment in each ensures that a high proportion survive. However, even in a k-selected species the optimum level of fertility will not in general be the same as the level that minimises the mortality of offspring.

Man is a highly k-selected species. Optimum fertility is unlikely to be vastly higher than the minimum number necessary to replace the parents. However, it seems clear that the selective optimum must be higher than present TFRs, and somewhat higher than the present replacement rate of 2.1. If average fertility were at the optimum, then parents with more children than average would have relatively few grandchildren. I don’t know of any recent figures on this point, but it seems highly likely that parents of 3 or 4 children have more grandchildren than parents of 2 children, contrary to the hypothesis that the optimum is around 2.

There is also a theoretical reason for expecting current fertility to be below the selective optimum. The reason is that the pattern of fertility has not yet recovered from a recent downward shock. Effective oral contraceptives only became widely available in the 1960s (and more recently in some Catholic countries), which is scarcely a generation ago. For the first time in history people who want to have sex but not children can reliably do so. The result has been a large increase in the proportion of couples having no children, or only one child.

But we would expect the pattern of fertility eventually to adjust from this shock. The mechanism for adjustment is that when average fertility is below the selective optimum, then those individuals who have more than the average number of children will contribute more to subsequent generations - they will have not only more children but more grandchildren. And if the propensity to have more children has positive heritability, then this propensity will be passed on, and the average fertility of the population will rise.

To illustrate this with a crude example, suppose that out of every 10 women in the present generation, 3 have no children, 3 have one child, 2 have 2 children, 1 has 3 children, and 1 has 4 children. The total number of children is 14, and the average per woman is 1.4 (which is within the current range of TFRs in developed countries). Now suppose that heritability is 100%, so that every female has as many children as her own mother. On these assumptions the average number of children born to each female of the second generation will be 2.57. Average fertility has almost doubled in a generation. This largely reflects the fact that in this model the most fertile 20% of women contribute half of all the children in the second generation (7 out of every 14), and we assume that the daughters from these families inherit their mothers’ high fertility.

Heritability of fertility is very unlikely to be 100%. However, it is also unlikely to be zero. With reliable contraception, fertility becomes largely a matter of psychology. Since factors of personality, however defined, are usually about 50% heritable, it is reasonable to suppose that the psychological factors influencing fertility are also heritable. (Even if the basis of heritability were environmental rather than genetic, fertility would still be transmitted for several generations, until the environment of the descendants had regressed entirely to the mean.) One thing we can say for certain is that women who have no children will have no grandchildren. So in an age of contraception any heritable factors leading women to be averse or indifferent to children will rapidly be eliminated from the population.

I conclude that over the course of another 2 or 3 generations, fertility is likely to rise back above the replacement rate, and populations in developed countries will grow again. If infant mortality does not also rise, at some point pressure on resources will lead governments to introduce measures to discourage fertility. Of course, over this time scale a lot of other things will have happened, and rising fertility may be the least of our worries.

I should mention that the main argument here is not new. It was stated many years ago by the physicist Sir Charles Galton Darwin (a grandson of you-know-who), but it has been generally neglected.


Posted by David B at 03:25 AM

Even if fertility is purely environmental, that just means we'll see an increase in fertility-promoting memes (which we're starting to see already, e.g. Mormonism).

Posted by: Oleg at August 17, 2003 12:28 PM

a few points.

on japan's density, one thing is that japan is the MOST DENSE COUNTRY in the world if you divide the population by ARABLE land. something like 20% of japan is really arable and flat. this is in contrast to bangladesh, with about the same population (give or take 20 million), but 80% of the land is arable (bangladesh is about the size of new york state, japan is the size of california).

on the "costs" of children-i don't think it plausible to assume that the state will continue the support our old to the same extent today. i think we might be in a sort of "sweet spot" for the aged in the first world, transitioning between a world with a low % of the old to one with a much higher %. our social systems still behave as if the over 65 were rare, because they were devised when they were. today they aren't. of course the retirement will have to be pushed up, but eventually, i think that older people will end up in the care of their children again because it is simply not fiscally possible for the gov. to care for 1/3 of the population.

of course, this does not take into account the effects of technology that might decrease the cost of aging (disease & supervisory care). but i suspect if we have 80-90 year olds that are sprightly because of technology-we will have 120-140 year olds that will need a lot of care to keep them alive, so the overall fiscal effect will be a wash.

finally-on the issue of selecting for fertility-i haven't thought too much in terms of genetic selection, but imagined a future where most americans were mormon ;) after all, the mormons have strong cultural incentives to procreate, since social esteem is to some extent connected to the number of children....

[My white brother oleg posted right when i posted, so we didn't mention moromonism through collusion ;)]

Posted by: razib at August 17, 2003 12:30 PM

There's a lot to say about this particular can of worms!

1. As Mormons become more educated, their fertility goes down too. Case in point, my ex-wife and her sister (3 kids total). And contrary to popular belief, Mormons put a lot of energy into education. There are a lot of crypto-Mormons and ex-Mormons in your world. They don't all marry their uncles when they turn 14.

2. Look at it as the global division of labor. Childbearing and raising is just plain bad business, especially for the woman. Not a rational choice at all. Solution: import children. Likewise, science is too much work for not enough money. Solution: import scientists and techies.

3. I read this in the Scientific American or somewhere. The ancient Carthaginians sacrificed some of their infant children to Baal. By keeping families small, inheritances weren't divided and various sorts of succession disputes were avoided. (The Ottoman Empire actually routinized the process by which the successful heir to the throne killed all his brothers). The goal here was to keep everything under the control of a very small, tight elite.

4. One advantage of an immigrant underclass over a native-born underclass is that they're humbler, and they also can be deported under certain conditions. The feelings of entitlement that unsuccessful native-born Americans have are an inconvenience to the controlling powers.

Posted by: zizka at August 17, 2003 04:55 PM

"The U.S. birth rate fell to the lowest level since national data have been available, reports the latest Centers for Disease Control and Prevention (CDC) birth statistics released...by HHS Secretary Tommy G. Thompson" (http://www.cdc.gov/nchs/releases/03news/lowbirth.htm).

BTW 2002 preliminary national and state birth data can be downloaded by going to http://www.cdc.gov/nchs/data/nvsr/nvsr51/nvsr51_11.pdf.

According to the preliminary data Alaska, Arizona, California, Florida, Hawaii, Nevada, New Mexico, and Texas are the states in which a majority of live births in 2002 were to minority women.

2001 national and state birth data can be downloaded by going to http://www.cdc.gov/nchs/data/nvsr/nvsr51/nvsr51_02.pdf.

Posted by: Proborders at August 17, 2003 05:25 PM

It will be interesting to see how the fate of Japan's fate (little immigration) compares to that of first world countries that are suplementing their population with large amounts of immigration.

Does anyone have any pointers to predictions on what the future fertility trends will be like among the high birth-rate immigrant groups to the US and Europe? I'm wondering how first generation rates will compare to third and fourth, but it seems like not enough time has passed in most cases to tell. What a complex cultural/biological question though...

Posted by: temporary_account at August 17, 2003 05:29 PM

i think it's only a matter of time before japan starts mass immigration... although in their case it'll probably be restricted to oriental looking people (which there are plenty of in china etc..)

david burbridge:

i think the current infertility in developed countries is a result of free choice, general prosperity et al.. not due to biological infertility per se (although the high amount of chemicals in the environment does contribute to low sperm count to an extent)... so even if certain people are demonstrably fertile today... their succeeding generations may not be demonstrably so because they may choose not to have children...

Posted by: turkey time gobble gobble at August 17, 2003 07:46 PM

Upper middle-class girls used to be socialized to get married and have children.

Now they are socialized to have careers.

Posted by: Gordon Gekko at August 18, 2003 06:56 AM

If you look at women's motivation for having children, and the rhetoric of pro-fertility groups like La Leche League and the Moral Majority, you can see that child-bearing is just plain not a free-market activity for women with choices. Women have kids in large part because of conventionalism, duty (family, religious and other), emotional compulsions, lack of options, etc. Women who want to kick back and take it easy don't want kids, women who want careers and independence don't want kids, people who want an expensive life style don't want kids unless they can afford nannies.

Posted by: zizka at August 18, 2003 08:29 AM

I agree with David. I've seen a similar analysis if I remember right, in the Economist--that birth rates seem dire now, but will even out as the women in their 30's have their "heir and a spare."


Posted by: David at August 18, 2003 02:07 PM

Gordon Gekko:
"Upper middle-class girls used to be socialized to get married and have children.

Now they are socialized to have careers."

I think this situation goes deeper than the women being socialized to do something. Women today can't necessarily depend on men economically as in the past. There's a 50% divorce rate. At the same time, since the 50's the American family's standard of living has remained the same largely due to women entering the workforce. In other words, a single income earner generally can't cut it anymore.

Women who do enter the workplace and become career women often often have to choose between going up the corporate ladder vs starting a family. And that's if they have a man. It gets progressively more difficult to get a man for many women after 25-30. Also, many men are frankly put off by the aggressive, take charge attitude of some of these career types- these are of course precisely the traits needed to climb the corporate ladder, too. Some men may even be put off by the fact that the chick has a good job while, ironically, many women might not want to marry men who make less than them. I am speaking, of course, in generalizations and not trying to be insulting. I think this is a real problem in the Western World- at least America.

Did anyone see 60min last night which discussed Susan Hewitt's book on the declining birth rate of career women? I know a lot of career women in their late 20's - 40+'s similar to the ones featured on the show who don't have a man and/or kids. I doubt I'm the only one.

Posted by: R at August 18, 2003 06:04 PM

I still don't think that you need abstruse explanations. Childbearing is economically a bad deal now and is only done any more for non-economic reasons. It used to be either an economic necessity or else imposed on women by custom, family, religion, and absence of options. The economic cost even to a married couple of childraising is enormous: besides cash out, there's lost opportunities, bigger house, better neighborhood (for schools), worktime lost by both parents, etc.

Like I said, import kids the way we import scientists (you guys).

Incidentally, I don't think that you need abstruse explanations for why women become nude dancers either. $40-$50 / hr. (not unusual at all) is a big inducement for a 20-year-old with no particular skills. Or for me, as far as that goes, though I'm not getting a lot of offers recently (probably because of agism.)

Posted by: zizka at August 18, 2003 07:16 PM

That upper middle-class career women are not producing kids is an alarming trend. These are the women that we absolutely need to reproduce, atleast for the good of this nation. Yet it's the pregnant single teenage mothers on welfare that demonstrate the greatest fecundity.

Dysgenic breeding is the single biggest (potential) dilemna facing the West. It's an even more contentious issue in America as it takes on a decidedly racial dimension. Yet Godless and co. assert eugenic genetic engineering as the solution, without considering moral/societal/theological implications. A more practical solution would a fundamental re-structuring of the welfare system. Cut back on ADC, single mother welfare benefits, child benefits, baby bonuses etc… all of which just provide further incentives for the underclass to breed. Provide financial incentives for the wealthy and upper-middle class families to produce more children – extended maternity leave, subsidized (even free) daycare as in Scandinavia, extended tax breaks for families with dependent children and the like.

Think about your future. Think about the nation and world that your children will inhabit. If present trends in immigration and (dysgenic) natality continue, we are no doubt heading for Murray's custodial state, in which a small cognitive elite in gated communities presides over the unintelligent, impoverished masses.

We need more intelligent babies! .... Of course, godless and razib can begin by doing their part ;-)

Posted by: An Impassioned Plea (Sen) at August 18, 2003 08:18 PM

Zizka, neither one of us has definitve proof regarding the validity of our theories to explain the dysgenic birth rates. As far as I can tell, each of our ideas are plausible. In fact, I think that not only are they plausible but mutually compatible too.

However, based on Hewitt's work, I suspect that my theory is more true for the majority of career women who never had kids while yours is more true for the majority of career women who have only one or two kids. In the latter, those couples have already made a decision to start a family even if there will be a backlash (of some kind) to the Mom at work. These families are just not deciding to have a lot of kids (maybe after weighing the negative cost paradigms you cite regarding child rearing).

Posted by: R at August 18, 2003 09:47 PM

In my post I deliberately didn't mention religion, as it is a complicated issue. It used to be assumed that Catholics always have a higher birth rate than Protestants, but now look at Italy.

It may still be true that people with strong religious faith (whether Christian, Jewish, or Moslem) have a high birth rate, because (a) they are less preoccupied with making money, (b) they take their religious doctrines seriously, which includes 'being fruitful', and (c) they tend to believe a woman's place is in the home, serving the man and looking after the kids.

If so, then religion is a 'heritable' environmental factor tending to increase fertility.

But the main point of my post (and C. G. Darwin's argument) is that in the long run you can't leave biology out of the equation. Even among 'career women', some want babies more than others, and those who want babies are more likely to have them. And in the next generation those babies will inherit some of their mothers' psychological propensities, including the desire for babies. And so it goes...

There may already be signs that the urge to procreate is beginning to prevail again. It is interesting that young actresses like Reese Witherspoon and Kate Winslet are having babies in their 20s, despite the huge financial drawbacks. And when fashion models like Kate Moss and Carolyn Murphy are drooling over their chubby brats, you know the times are a'changing.

Posted by: David B at August 19, 2003 03:19 AM

Part of my argument is simply that whenever a woman has kids, it's for non-economic reasons. (In Madonna's case, Lourdes seem to be an expensive prestige accessory). Here we are on a mostly-libertarian site, and we're asking women to make sacrifices for the sake of society.

This is a real glitch in contemporary political debate. The same Republicans who gloat about our booming economy and high standard of living get all pious about family values right on cue, but a lot of our prosperity depends on two job families, and the conservatives (husbands and wives) I know who dedicate themselves to being parents end up losing one enormous step on the income ladder to do so.

Posted by: zizka at August 19, 2003 11:47 AM

So have any countries actually been successful in boosting birthrates in recent history? I think someone mentioned before France's failure at pronatal policy...

I know the libertarian streak leaves most GNXPers against any sort of social engineering. I'm pretty pessimistic about the potential remedies myself, both because of problems with said potential solutions, and because most would be lightyears away from zeitgeist-approval anyway.

Sigh. Any indiscrimate pronatal policy would just exacerbate current trends (and is seen as unnecessary when immigration is available). Any discriminate one would be be evil.

Perhaps some small gains could be made under the feminist banner. For example, forcing companies to provide maternity/paternity leave and penalizing any discrimination associated (just an extension of the current hate-crime policing).

Is there any hope on the current political platter? (Or even on a hypothetical one.)

[ I'll stick to my consolation in the potential of a transhuman future (organic or computerized) to wash the problem away. ]

Posted by: temporary_account at August 19, 2003 02:06 PM

temporary account:
"So have any countries actually been successful in boosting birthrates in recent history? I think someone mentioned before France's failure at pronatal policy...

...[ I'll stick to my consolation in the potential of a transhuman future (organic or computerized) to wash the problem away. ]"

I am unaware of any governmental policy that has been succesful at changing cultural tendencies regarding fecundity. Hopefully, GC and his constituents will be able to accomplish the GE task in this century. I am betting they will do so and think GE at the start of this century is where electricity was at the start of the last. If that is correct then mankind is on the verge of its greatest achievements. I have considered the ethical problems (which probably deserves more space and time than here). I think there will be a period of strife due to the GE that will give way to a longer, greater period of stability and progress.

Traits like baldness, shortness, shortness, fatness, stupidity and, yes, even ugly appearance might be eliminated from the general population without Hitler style tactics. What reason will ther be for White Nationalists to exist since race itself will be completely irrelevant? Since eventually all women will be really hot, men will end up choosing women for purely their other characteristics (like inner beauty). Maybe all guys will be able to bench press at least 250lbs without working out much. Mankind will finally be able to live in a Lake Wobegon scenario where every child is above average (in terms of intellect). I am probably getting carried away here, but I really feel that this is the true potential with GE. GE is always represented as evil in the media (Star Trek's Kahn or various analogies to Hitler). I have ZERO problem with China getting to GE first if the US and the rest of the West are cowed into complacency on this issue. We humans have always done well in emergency situations. When the US and the rest see what China will do with GE, that will spark a massive surge in interest in the stuff here and, ultimately, the rest of the world'll catch up.

Posted by: R at August 19, 2003 07:30 PM

Traits like baldness, shortness, shortness, fatness, stupidity and, yes, even ugly appearance might be eliminated

Going to eliminate shortness twice ;-)? But seriously, all of these except perhaps baldness are traits where people are measured against other people. Moving the average isn't going to change the fact that some will be fatter, stupider, shorter, or uglier than others. And perceptions will probably change, smoothly, so that eventually we could imagine that a 6 foot tall man would be considered short, or a 120 lb woman considered fat, etc. In fact something like this has arguably already happened - we are much taller and smarter than we were a thousand years ago.

Posted by: bbartlog at August 20, 2003 05:37 AM

"But seriously, all of these except perhaps baldness are traits where people are measured against other people. Moving the average isn't going to change the fact that some will be fatter, stupider, shorter, or uglier than others. And perceptions will probably change, smoothly, so that eventually we could imagine that a 6 foot tall man would be considered short, or a 120 lb woman considered fat, etc. "

Forgive me for getting a little carried away. You are right that there will always be variation. Just like there will always be evil and what not... GE obviously won't get rid of all human suffering. Plus, there is obviously an environmental component to almost everything I've mentioned.

However, GE will 'level' the playing field to a large degree. More people will be bunched around the 'average' (i.e. value for height, strength, 'looks' etc...). The 'averages' will also be presumably better from a qualitative standpoint than our current 'averages'. For example, perhaps we can eliminate the midget phenotype from the population with GE. Maybe we can eliminate whatever genetic component to morbid obesity there is in the population. GE won't be a cure all for every fathomable inequality- but that does not mean it should be considered a failure when we get it.

Posted by: R at August 20, 2003 08:40 PM

The point about birthrates is that they can change *very* fast

France is a good example - in 1940 it had the lowest birthrate of any European country

By 1950 it had the highest: today there are more French in Europe than Brits or Italians - a statistic that would have amazed anyone in the 30s or 40s

Posted by: ToOmUchWoRK at October 12, 2003 12:32 PM