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Predicting the global population
00:08:58
Predicting the global population: does anyone really know what’s going to happen?
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A
Hello and welcome to More or Less on the BBC World, investigating the numbers in the news and in life. I'm Jan Wong. This week, how can a woman not know she's pregnant?
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Honey, I got on the roller coasters and there's big signs saying that pregnant
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women should not be on them.
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Somebody help me, please.
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An exciting day at the amusement park will turn into a nightmare roller coaster ride for one woman. This is the real story of a woman who didn't know she was pregnant. Just how uncommon is it for a woman to give birth without knowing she was pregnant? But first, and still in a roundabout way, on the subject of babies, the United Nations Population Fund recently published a report describing the world's aging population.
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Today we have one in nine persons age 60 and over. But by 2050, it'll be 2 billion persons. One in five will be 60 and over. And by that time, there will be more older persons than those under age 15 years. And this is no longer just a developed country phenomenon. It's happening faster, in fact, in developing countries. But most of them are not really prepared for the growing numbers of older persons.
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That's Dr. Anne Pauliczko from the UNFPA. She says we can be pretty confident about the numbers.
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We can be very certain about the numbers for 2050 because persons who will be age 60 in 2050 are already born. So this is not speculation.
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Fair enough. But in the longer term, the figures aren't going to be dominated by the likes of you and me. It's the birth of new people that will have the largest effect on future statistics. And here's where it gets interesting. For a long time, statisticians have observed something which they call the demographic transition.
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The demographic transition is a shift of birth and death rates from high levels to low levels in a population. And that usually is a result of economic and social development. You have several stages. Typically, we speak of four stages. We have the first stage as high birth and high death rates, where there's slow population growth. Then we have the second stage where you have high birth rate and falling death rates because of improvements in food supply, sanitation technology, basic health care, education, et cetera. And that's where you have high growth rates. Then stage three, declining birth rates and relatively low death rates. And this is characterized by slow growth rate of the population. The growth begins to level off. And then stage four is where you have low birth rates and low death rates, and consequently a low population growth.
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So as countries get richer, their fertility rates drop. And it's long been assumed that that's the way it will continue to go. But what if it doesn't? Professor Jane Falkingham is director of the ESRC Centre for Population Change at Southampton University in the UK.
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Historically, for the last 20, 30 years, fertility has been falling right across Europe. But actually, if we look at the most recent period, say across the last 10 years or so, we see rises in fertility in the most advanced countries. And in particular, if we look at countries in Scandinavia, for example, they now have the highest fertility rates in Europe, whereas in the countries we might have thought of having the highest rates, such as Italy and Spain, they actually have the lowest rates of fertility. The work that's been done around this is actually by Francesco Bellari, who's a new professor at Oxford University, so you might like to go and speak to him about it.
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My name is Francesco Bilari. I'm professor of Sociology and Demography at the University of Oxford. Just after the year 2000, suddenly fertility was on the increase in several societies.
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The pattern that you've observed is largely for a very few reasons.
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Rich countries.
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Could it be that that's just due to immigration into those countries?
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We did some calculations and basically the new change is not only due to migration. Also, the locals are changing also because it's the basic structure of institutions in society that is changing. Daycare is developing. Other solutions are basically allowing women to lead a career and be mothers.
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So the indigenous population in these few countries is also increasing its fertility rate?
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Yes, indeed. Demographers used to be the lucky ones because we thought that it was easy to forecast population change. I think that's no longer true. It's no longer true at the global level because recent fertility trends are showing that the future is much more uncertain than we thought. So, for instance, there may be a complete change in the ranking of fertility levels within the world.
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If you're an evolutionary biologist, and as it happens, I am, you might not be surprised by all this. The idea that the wealthier we are, the fewer kids we have is, when you think about it, very odd indeed. Normally, natural selection produces individuals who are very good at converting their resources into lots of fertile descendants. It's a demographic paradox that in the past few centuries, developing societies haven't been filled by families who raise as many kids as they can possibly afford. Almost the opposite, in fact. But putting Darwin to one side, how much difference might the recently observed uptick in fertility in highly advanced countries actually make to global population projections? Not much, according to Dr. Paul Lichko at the UN.
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We don't expect it to be that significant?
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Maybe she's right. But then again, we've actually got population
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projections wrong consistently over the last 50 years. And this is partly because we've underestimated the improvements in mortality, particularly at older ages mortality. So we've got more people surviving into old age and living for longer than we previously forecast that we would have. But also we've not been very good at spotting the trends in fertility.
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Of course, one day we'll know whether our population projections beyond 2050 were accurate, whether the so called demographic transition disappeared, or whether huge leaps in life expectancy changed the picture completely. But forecasting population will always be a highly uncertain Science.
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The latest UN projections, which were published in 2010, predict if we take a medium range projection, that the world's population will grow to about 10 billion by the end of this century. But if we take an upper range, it could grow to 16 billion. Whereas the lower range shows the world's population actually shrinking down from its current 7 billion to around 6 billion by the end of the century. And I think that the big issue really in terms of how fast the world's population continues to grow in is how fast fertility comes down.
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In Africa, Professor Jane Falkingham. Now, from future babies to unexpected ones. A recent news report told the story of a Fijian soldier serving with the British army in Afghanistan who gave birth having not realised she was pregnant. That raises an obvious how often does this kind of thing happen? An obstetric consultant was on hand to give BBC News the answer.
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Interestingly, it may not be as uncommon as we think. There was one study from Galway in Ireland, where they have a relatively high rate, about 1 in 150. So actually not that uncommon.
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Did you catch that? In Galway In Ireland, 1 in 150 pregnancies is a total surprise to the mother. If that's true, then what on earth is going on in Galway? Well, the. That research was carried out by Claire Tyne, a clinical psychologist.
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Our study wasn't looking at women who are totally unaware they are pregnant. Our study was looking at quite the opposite. Women who are very much aware they are pregnant but conceal the pregnancy from those around them, from their family, from their partner, from their friends. And we were looking at why do these women do that? And obviously it was a crisis pregnancy or unplanned pregnancy. Our study wasn't looking at women who were caught unawares that they're pregnant. These women were aware and just hid the pregnancy.
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Claire Tyne. So if the true figure of unknown pregnancies isn't 1 in 150, what is it? Well, it's hard to say, but we have found some research in Serbia that suggests that about 1 in 7,000 might be more realistic. And that's all from me this week. Do please keep your questions and comments coming more or less@BBC.co.uk I promise we do read every single one and we're always on the lookout for statistical stories. If you spot one, let us know. Our website is BBC.co.uk more or less where you'll find some of our best stories from previous programs. I'll be back next week. Until then, goodbye.