You wouldn't think it to look at our skyrocketing global population, but many parts of the world are experiencing serious falls in fertility. A country's fertility rate is the average number of children born to a woman over her lifetime. In most developed countries, it needs to be 2.1 or higher if the number of newborns is to compensate for citizens who die. In developing countries, where death is a more frequent visitor, this replacement threshold is even higher.
The problem is that declining fertility is intimately linked with a country's economic and social development. As a result, more than half of the world lives in areas where fertility rates have fallen below this crucial threshold. It's the same situation in the UK, Australia, Japan, China, Brazil, Russia, Canada and more. Some believe that these processes are irreversible, with increasing prosperity inevitably leading to diminished emphasis on childbirth.
But Mikko Myrskyla from the University of Pennsylvania thinks differently. He has found that the most developed countries have actually reversed their falling fertility rates, possibly by improving gender equality and making it easier for women to raise families while enjoying successful careers. The result is a graph that looks like a reverse tick, with a small upturn in fertility rate that only becomes evident when looking at data from the dawn of the 21st century. At the most advanced stages of development, it seems that babies make a comeback.
Now for those of you jubilantly punching the air at the prospect of fewer people, a bustle-free life and a less taxed environment, it's worth considering why fewer births is a problem in the short term. Falling fertility rates mean ageing populations. That means that the country will be served a shrinking workforce, while having to pay greater healthcare costs due to rising levels of chronic disease and disability.
If fertility rates fall too low, as is the case in Russia and Japan, the population will actually start to shrink, again with important social and economic consequences. Immigration can help to offset that loss, but as countries like the US and the UK demonstrate, immigration brings social strife of its own.
So in the long term, fewer people might be a good thing, but in the immediate future, it means big challenges. In that context, Myrskyla's data provide a silver lining in an otherwise gloomy picture. He compared the fertility rates of 107 countries in 1975 with their scores on the Human Development Index - a measure of the level of development that takes into account life expectancy, literacy, education and standards of living. He did the same for 140 countries in 2005.
In both years, Myrskyla found that the greater a country's HDI score, the lower its fertility rates, but only up to a point. At scores of 0.9 or over (and the range goes from 0 to 1), the trend reverses so that women from the most developed countries have , on average, more babies. This trend only became obvious by looking at the more recent set of data for in 1975, no country had reached the stage of development where fertility rates pick up again. Then, the top score was 0.887, while Australia is currently in the lead with 0.966.
The upturn is small but significant. If a country's HDI score is between 0.9 and 0.92 (as is the case for South Korea or Germany), the average fertility rate is low enough at 1.24 for the population to halve in size every 40-45 years. However, countries with the highest scores (including Australia and Scandinavia) have an average fertility rate of 1.89 - not quite the replacement level, but close enough that small levels of migration can sustain the same population.
Myrskyla saw the same trend when he focused on individual countries over the last 30 years. There were a few exceptions but in general, as countries became more developed, babies came back into fashion. In the US, falling fertility reversed in 1976 at an HDI score of 0.881. In Norway, it happened in 1983, at a score of 0.892. Myrskyla reckons that the critical point is around 0.86 - beyond this stage of development, an extra 0.25 points on the HDI score translates to roughly one extra baby for every woman.
The big question, of course, is what's behind the reversal? It certainly seems to apply to a diverse set of cultures and the exceptions (including Japan, Canada and South Korea) are hardly that similar. Myrskyla thinks that high HDI scores reflect societal changes that make it easier for women to choose to have children. As equality becomes more strongly felt, women get a better education, earn more jobs and command higher salaries. That makes it easier for them to cope with the financial drain of children, and for them to successfully take time out of the rat race and re-enter later on.
It's possible that rich east Asian countries like Japan and South Korea have failed to buck the fertility trend because they have failed to address the challenges of gender equality and work-family balance that other countries have begun to tackle. Still, that doesn't explain Canada. In a related editorial, Shripad Tuljapurkar suggests that the HDI itself may be to blame. It doesn't tell us anything about whether development affects men and women equally, and in that respect, the Gender Development Index (GDI) maybe a more useful measure.
All in all, Myrskyla's results paint a slightly rosier outlook for much of the world. As he writes, "As long as the most developed countries focus on increasing the well-being of their citizens, and adequate institutions are in place, the analyses in this paper suggest that increases in development are likely to reverse fertility declines--even if we cannot expect fertility to rise again above replacement levels." However, many countries that are already facing falling fertility rates have a while to go before they cross the 0.86 threshold. In some of these places, keeping fertility rates below the replacement threshold may actually be in their best interests.
Reference: Nature doi: 10.1038/nature08230
More on fertility:
- The heavy cost of having children
- Did conflict between old and young women drive origin of menopause
What country is that outlier near .92:2.8?
Let's all remember that the fertility rates SHOULD be dropping, as the planet is not equipped with enough resources to sustain a population our size with decent standards of living.
China (which always does things in a big way) has recently realized the impact of the one child policy in the size of the work force relative to the aging population. I don't have the stats on hand (and am fluish) but it's jaw dropping. That being said, while it does create social problems for a generation, in the long run our planet needs fewer not more people using its resources. Most other moms I talk to consider more children, whether they have 1, 2, 3 or more kids. After each one the question arises as to whether to expand the family and it's usually (not always) with a tinge of regret when the decision is made not to have any more. So it makes sense to me that with more gender equality, affluence and social support that decision would be to go for 1 more for a number of families.
Did the authors check for a correlation between increasing birthrate for high HDI values and migration rates? Perhaps this is a tabloid trope, but there's a possible logical progression from better quality of life -> more desirable location for immigrants from poorer countries -> increasing birthrate as migrants reproduce at the rates similar to those normal in their countries of birth. The dates struck me as interesting, along those lines, but then they also coincide with the start of better employment conditions for women.
I really need to get myself back to university, so I can get journal subscriptions.
Fertility rates declined in developed countries because the environment and social conditions changed radically within only a few generations. Genetic (or memetic) evolution didn't have enough time to act to get people to maximize their fertility rates again. Now you have various sub-populations in probably every country that have a higher fertility than the rest of the population. So there is always going to be an eventual trend towards higher fertility rates as those sub-populations expand in number. If one religion tells its adherents to have more children then they will propagate at a faster rate than the other religions. It's all just differential natural selection at work. People who say most countries are going to trend towards a replacement fertility by 2050 are just plain wrong.
I also wouldn't equate having a higher fertility rate with good economic prospects. There are many poor countries that have high birthrates, but they are basically just adding to the sum total of human misery with each child. I think it isn't necessarily a bad thing to have a declining fertility rate in developing countries. Productivity increases and this can cause an increase in economic prospects for those remaining. Japan has been developing robots to service its elderly population, for instance. From a utilitarian standpoint I think reducing human suffering entails limiting the amount of conscious minds that are born into the world. I'm a libertarian, though, and dislike the idea of limiting people's birthrates. However, I assume that radical life extension will be more likely within my lifetime. So encouraging people to have fewer children may be paramount to ensure that our society doesn't collapse.
You seem to downplay the importance of the long term. If avoiding big challenges is a priority, I can't imagine that increasing fertility rates will succeed at that. If the short-term economic challenges are avoided, they'll only open the way for other kinds of big challenges. What are some alternative solutions to the impending human overpopulation problem? If we make an effort to increase our fertility rates in the short term, it would be wise to have a plan to deal with the consequences. What should be our plan?
If you're worried enough about society collapsing to be willing to do anything about it, you're no libertarian. (I've skipped a few steps in the derivation. They're left as an exercise.)
The immigration -> fertile-subculture notion is interesting. I wonder if it can be tested with the data available. I think Israel has an unusually high immigration rate; what of the other outliers?
> I think Israel has an unusually high immigration
> rate; what of the other outliers?
IMO, Israel is an outlier because it is a very heterogeneous society, which is classified by most Israelis into three main groups: Arabs, religious Jews, and secular Jews. The first two groups have much higher fertility rates than the last group for cultural reasons.
That map is wrong. There is no way Muslim nations like Kazakhstan and Uzbekistan are having below replaceable TFR. TFR is around 2.3 for Kazakhstan and 3.0 for Uzbekistan. It is wrong for Bolivia also.
Most of the questions I would ask have been asked. I read an article about Italy which I did not understand. Italy has a declining birth rate to the point that there are not enough young Italians for the needed jobs. Read on down and the article told how young Italian men live at home up to around age 30 because there is no work for them. Somehow this does not compute!
Paul Colinvoux, in "Fates of Nations", argues that people tend to have the number of children they think they can afford. Children of affluent parents are very expensive, whereas children of poor parents are both absolutely and relatively less expensive. Therefore poor people tend to have more children than rich people. I've read somewhere that immigrants tend to overestimate how rich they have become, and have more children than one would expect. I think this is the case in the USA.
There are serious problems with the Nature paper, including a substantial statistical bias. See my guest post on the Stubborn Mule:
Further to Mark's comment, Mark has now done a follow-up post describing further flaws in the paper. Here is a summary of his findings: http://mule.posterous.com/dodgy-analysis-in-nature-fertility-not-really