7 Billion: Understanding the Demographic Transition

On the 31st of October we will officially reach 7 billion people on the earth. Over the next week or two we'll be talking a lot about population issues, and I wanted to start by doing a light revision of an article I wrote some years ago about a concept a lot of people don't grasp very well - the idea of demographic transition and what it means.

The term "Demographic Transition" describes the movement of human populations from higher initial birth rates to a stabilzed lower one, and seems to be a general feature of most societies over the last several hundred years.

Initially, birth rates are high, but so are infant mortality and other death rates, and population numbers may rise, but they do so quite gradually, kept in check by high death rates. In Europe and North America, the Demographic Transition occurred over more than two centuries, and extremely gradually, as hygenic practices changed, medicine improved and other factors lowered death rates.

Women grew up noticing "hey,five kids aren't necessary - I can have three and be assured of getting most of them to adulthood." Thus, the average TFR (that's the total fertility rate) dropped steadily from 8-6 (across Europe and the US) to 2.8 and then down further in the late twentieth century. Now the developed world has an average TFR of 1.8, below replacement rate.

This began in the 19th century in the rich world (visitors to the colonies or in America's earliest history were stunned by the high birth rates of American women, who had a TFR over 8 in the late 17th and early 18th centuries).

The demographic transition, however, didn't happen in much of the Global South until the mid-20th century or later. In general, the Global South has undergone a much faster demographic transition than the rich world did - in many cases, radical change has come in less than 50 years. And because in many places in the third world, there has been considerable instability, the factors that lead to a transition haven't been consistently available in many places - that is, it is all the more remarkable in many ways that so many areas have seen such a dramatic decline in total fertility rate.

We all know that rich world nations like Japan and Italy have a TFR well below replacement, but more than half of all poor nations are below replacement rate, and most of the rest are following. The highest reproductive rates are in Sub-Saharan Africa, and those too are following the pattern of other poor nations, but are 20 years behind them. Subsaharan Africa now has a TFR of 5.0, down from 6.3 in 1990 - a huge drop. Latin America is now at 2.6 as a whole, and has nearly halved in merely 20 years. All over the world, population rates are generally falling much faster than even the most radical demographers expected.

What's most interesting about the demographic transition is that birth control, while an important factor, isn't as huge a part of the project as you'd think. In America, for example, we dropped our birthrate to 2.8, before disseminating birth control information was even legal or widely available. Despite a widespread increase in birth control availability after World War II, American birth rates rose well above what they were in the era of the Comstock laws when birth control was illegal.

Birth control is estimated to affect about 15% of demographic decline - but that's a comparatively small percentage. In their book _Understanding Reproductive Change: Kenya, Tamil Nadu, Punjab, Costa Rica_, editors Bertil Egero and Mikail Hammerskjold observe that fertility change seems less closely tied to birth control access than to cultural pressures, education and political power for women, how many children are needed to have surviving children into adulthood, and the economic role of children. That does not mean that birth control doesn't matter, but it should be generally heartening to those who worry that industrial medical care may become less available in an energy or economic decline - yes, women should have full access to birth control and medical care, but mostly they need education, political power and medical care that allows their children to live past infancy, so that they feel less pressure to have children to compensate.

While many women in the global south express a desire for fewer children, in many cases people make fairly rational choices, based on their personal economics, their personal situation, their need to have a child of a particular sex, their need for workers, their need for someone to help them in old age. Time and time again, studies like Pritchett's on "Desired Fertility" demonstrate that women worldwide, in every situation, mostly make fairly rational choices for themselves about their family size as long as they have basic rights and power to control their bodies.

The ongoing demographic transition is not, as it is commonly thought, primarily a feature of the rich world. Poor nations as diverse as Albania, Costa Rica, Cuba, Sri Lanka, Thailand, and the Philippines have rapidly declining birth rates. And what factors do most of these nations have in common? Generally speaking, basic commodities are widely available - that is, people get to eat. For example, a 1996 USAID report documents a direct link between subsidizing rice in Sri Lanka and a drop in TFR from 3.1 to 2.0 in less than a decade.

Basic access to medical care is widely available. Women have high literacy rates and political power. Women are comparatively well protected from rape, and can choose their husbands. A 1994 study by Yale Economist Paul Schultz fournd that female literacy was perhaps the most defining factor in TFR in poor nations. In India, Kerala, with a 100% female literacy rate has a 1.7 TFR, compared to a 4.1 TFR in regions with a 30% literacy rate

But, all the individual factors together add up to what Jeremy Seabrook rightly observes is "security." If kin are the only safety net you have access to, then you will have children as a form of security and wealth. If there are other options, you will turn to those. Education represents the possibility of work if a husband dies, knowledge of laws, access to information - it is not in itself a reproductive constraint, but an aid to security. What most people want when they have children is security, pleasure and comfort. If 2 children can do that as well or better than 5, they will have two.

As Maria Mies and Vandana Shive point out, for a woman in many parts of rural India, it is still necessary for her to four children to be certain to have one adult child available to support her in her old age. In Nigeria, a six year old contributes more than they eat, and a 12 year old does the work of an adult, while eating less. If we want to encourage families to have fewer children, the need for those children is something we must address - as well as the power to decide.

We know that there is a profound connection between population and poverty, but we also know that there are poor societies that have managed to make a huge reduction in TFR.. The evidence for whether high TFR causes poverty is, at best, mixed. For example, prosperity in India has grown dramatically despite a fairly high TFR. Even Paul Ehrlich, famed Zero Population Growth advocate and author of _The Population Bomb_ and _One with Nineveh_ admits in the latter volume that the answer is extremely difficult to sort out, and that there's limited evidence on that subject.

Generally speaking, the demographic transition occurs as a result of a certain degree of wealth - it is certainly moved along by money for infrastructure improvements such as water systems and sewers and birth control. But very poor nations can and sometimes do prioritize these solutions, for example, desperately poor Tanzania uner Nyerere did so, and saw its level of wealth rise while its population was still increasing. The US dropped its TFR from above 8 to below 4 without making major widespread infrastructure changes.

What is true is that population instability does create poverty - for example, the death of 20 million people in Africa to AIDS has left economies stripped, societies filled with children and elderly people caring for them, while the central working generation is ill and dying. Into this situation comes greater poverty, lower educational levels for women, despair, greater need for young women to become prostitutes, and a rising birth rate in some places, massive economic gaps in others. A slow stabilization of population is probably better than wild fluctuations brought about by short term conditions.

The factors that work to limit population growth deserve some greater attention than my quick summary above, because they way they seem to work is as important as the fact that they do. They give us a sense of what kind of society we'd need to create in order to achieve population stabilization, so let's give them some attention.

The first factor, education, works in several ways. Literacy for women benefits families in a number of ways. It increases her health (a literate woman can read material about health and hygeine practices) and the health of her children, it increases her family's security (if her husband dies, she can get a better job), it increases her desire to see her children receive education and it increases her political power - she can read and understand national issues and participate in them.

Mandatory education for all children serves to remove children from the labor pool, and makes children not producers, but consumers, and thus parents are forced to view their children in that light - if children become an economic burden for longer, than we have to gauge whether they are affordable.

Food security, including price supports, and many other possible programs improves the likelihood of having healthy and non-disabled infants, it makes it less necessary to set children to work finding food, and it makes it possible for women to reserve time for public participation and education - a beneficial circle.

The security of elderly people and the disabled can be assured in a number of ways - public support a la social security is one. Traditions of family obligation are another - were we to treat our obligations to aunts and cousins as strongly as we treat those to sisters and parents, as some societies do, the requirement that individuals have more children is greatly reduced.

Basic health care and hygeine matter because they reduce infant and child mortality, reduce harm in childbirth, and enable women to take advantage of contraception when they want it. They also make childbearing less dangerous, which paradoxically reduces birthrates, because it increases family stability and reduces rates of disability and death within families that drive children out to work at early ages.

Another powerful factor is sexual practices in regards to rape, marriage, prostitution and birth control. Birth control, is, surprisingly, at times the least important of these factors. Discouraging men from seeing prostitutes in the Gambia reduced fertility rates significantly, as prostitution is generally a result of extreme poverty as most prostitutes can't afford contraception. In Libya, enforcement of existing rape laws was found, to reduce TFR signficantly. All of these factors are associated with the status of women, and the more cultural and political power women have in a society, the fewer unwanted pregnancies she has. These are factors that generally speaking are mended by cultural pressures - for example, in the US, where rape and prostitution are huge problems, how many of us sit down with our sons and not only discuss rape in detail, but talk about prostitution?

Freedom from war is perhaps the most underestimated factor. People who fear that their children will be taken from them by the state or killed by routine violence have every reason to have extras to ensure the survival of at least some of their children. Because war disrupts security, it is hard for families to make rational choices in the face of war. Genocide and racial conflict encourage the harmed parties to increase fertility rates to compensate and outpace other communities (see the birth race in Israel and Palestine).

Similarly, the state (or other instigators) have every incentive to encourage women to have as many children as possible in the interest of the state if they are needed to fill armies.

Like war, nationalism itself represents a serious incentive to have more children. Low TFR nations like Japan and Italy that also have strong anti-immigrant sentiments have experienced periodic public calls for a pro-fertility campaign. One of these days, such calls may work - we know that building on racism and hostility to the other is a good way to set up fertility races, but has unfortunate outcomes.

It may sound as though achieving a worldwide population stabilization is impossible -as though we must fix all human problems first. But that's not the case. In fact, it turns out that the total investment in reducing world fertility levels voluntarily is comparatively low. Best of all, most of the changes are human powered, low input, and comparatively cheap. That is, most of what would be required would simply be to prioritize these things.

Fossil fuels, for example are not required to have small local schools, small amounts of fossil and renewable energy are required for some basic medications, but as we can see from the timing of the European and North American example, the demographic transition in the rich world was mostly not a product of fossil fuel based medicine, but a result of infrastructure improvements in nutrition, cleanliness and access to food and water. Safe water, greater food equity and a host of fairly simple good thing - insulation from wild food price fluctuations on global markets, solar water pumps and training in handling human wastes are all things we could prioritize as a society if we chose.

Political power for women is not a product of fossil fuels either, but a cultural change that can be brought about in lower-energy societies - if we make it a priority. Can we do this in the face of peak oil and climate change? If we prefer to have their impacts be as mitigated as possible, we certainly would do so.

The demographic transition is not a product of wealth or cheap energy in large quantities - we can see that by viewing the history of demographic shifts in Europe and the US. Instead, it is mostly about enabling people to make different reproductive choices, and supporting those choices - it requires no coercion, no high energy infrastructure, and is comparatively cheap to achieve.

We are going to need to make massive changes in our infrastructure one way or another. Too much of the discussion of what to do about peak oil and climate change has been about trains and carbon credits, renewable energy, new economies and extraction technologies. And as long as the conversation stays there, we'll be missing the point. Because ultimately, people care most about being fed, having their kids live to grow up, having safe water, basic housing, etc... As long as we continue the "growth and replacement" model of discussion, we'll miss the basic point - that what we need most to concentrate on is health, education and social well being. This would be a radical shift in world priorities - but in many ways a less costly one than most of the shifts being advocated by those who claim will we make a smooth transition to a renewable energy economy.

The thing is, political power for women, food equity and access to clean water and freedom from war and rape are good things in and of themselves - they benefit everyone in the community. That they also help stabilize a world population that is in part straining every resource we have is just another factor.

I've written previously about how UN projections that we will reach a population of 10 billion by mid-century don't adequately take into account the resource constraints we are facing. One way or another, indications suggest that we will see some population declines. There are two ways this could happen - we could have fewer children by choice or more death. It doesn't seem like a tough decision to me.



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Excellent, Sharon. Amen.

So the solution for Yemen is to convert the entire country to a different religion that doesn't treat women as if they were livestock? Yeah, right...

By Craig Thomas (not verified) on 20 Oct 2011 #permalink

While I don't dispute your assertion that access to birth control is the least important of many factors when it comes to declining TFR, I am baffled as to how women without access to birth control manage to avoid getting pregnant. No explanation is forthcoming in this essay. In past societies, people used dangerous abortions and infanticide. Assuming that human females have not acquired new powers over their ovulation in the past 100 years, what is your explanation for control of fertility in the abcense of birth control? I don't believe for one second that teenage girls choose not to have sex... Having been one and all.

Very interesting post, much hard work from OP, thanks. Note however the resurgence of conservative religious attitudes and power, which pushes many to have more children than otherwise. No time to be complacent about population growth problems.

This post was so heavy duty, so to speak, that I'm still contemplating it. I did, however, share Aimee's question as I was reading the comment on birth control. If there's little or no birth control, what helps bring down the pregnancy rate? Abortions, medically performed and legal or not, just don't seem to happen enough to explain the lower birth rates. In my line of work, with teenaged boys and their families from at-risk communities in the Boston area, I can't recall the last time I even heard the word abortion (though granted, I'm not a clinician and the boys are one person removed from the girls, obviously.)

Do women simply cut back on sex enough to matter to the statistics as other factors such as education come into play?

By Stephen B. (not verified) on 21 Oct 2011 #permalink

Perhaps me saying "little or no" birth control is not accurately recounting what you've said here Sharon. Sorry about that. I guess I was writing my previous comment with Aimee's thoughts in mind as much as those in your essay. Still, I look forward to your comments :)

By Stephen B. (not verified) on 21 Oct 2011 #permalink

I think the point is that when women are secure, they: 1)don't marry as early in life (or have sex as early in life for that matter) because their survival is not dependent on having a spouse and 2)they have the security to say no to unwanted sex. For example, consider that the normal age to marry in the US in the mid 1800's was mid-teens for girls (think 15/16 yrs old) and most women would have had at least 1 child before 20. It isn't hard to have many children when you have 30 years of potential childbearing. Now, women start having children closer to 30 and the birthrate is correspondingly lower (many other factors, including birth control, clearly factor in here too).

By FarmerAmber (not verified) on 21 Oct 2011 #permalink

I'd agree with that FarmerAmber.

Thanks :)

By Stephen B. (not verified) on 21 Oct 2011 #permalink

Really interesting. I have wondered how recent advances in malaria prevention, etc. might affect population in 3rd world countries, and the idea that not needed "replacement" children might reduce birth rate makes some sense. I am college educated in the U.S. and had my first and only child in my late 30's. It has occurred to me on more than one occassion that I don't have a "back up", but with resources to feed, educate, and otherwise protect him, the likelihood of losing him is small relative to people in other circumstances. I agree that access to birth control is under rated in this essay, but also that not needing to marry young for protection and support by a husband does partially answer the question. However, in my case, access to safe, legal, affordable birth control was key in my ability to wait until my 30's to intentionally reproduce.

By Waiteforit (not verified) on 22 Oct 2011 #permalink

There was a mathematical study, by Sokol, I think, back in the last century, which found the most effective method of slowing population growth was by lengthening generation time. That is, women having their first child at a later age.

Paul Colinvaux, in "Fates of Nations", argues that people have the number of children they think they can afford. Cost of children for poor people is generally low, so poor people tend to have more children. Cost of children is relatively greater for affluent people, so they tend to have fewer children. I've seen comments that poor immigrants into the USA tend to have more children that old inhabitant families. I wonder if it is a matter that they do not understand that, now that they are more affluent, they cannot afford so many children.

By Jim Thomerson (not verified) on 22 Oct 2011 #permalink

So I'm right on track to have the 7 billionth baby on Earth... We keep joking that his middle name should be 7B. :)

I like that you can have a rational discussion about population pressures without veering off into crazy anti-child territory. I mean, of course you can, you know how to distinguish between large-scale trends and personal choices. Good post, as usual.

Being a journalist based in Kenya, i can say i greatly appreciate the insights on tackling population especially on using education key to achieve this end. my past work has been on maternal health http://westfm.co.ke/index.php?page=news&bid=798 and http://www.westfm.co.ke/mobile/index.php?page=news&id=1482. Some of the insights i have used and attributed to a write i will gladly share with you now on a local perspective to Kenya.

Hello Sharon,

Thanks for this. It provides me with lots of new information to mull over.

I wonder what you make of the argument made by Dan Quinn and others that human population acts like the population of any other species in that it relates first-and-foremost to the amount of food available to it - only in the human case, some of us have figured out how to use agriculture to artificially increase our carrying capacity (for the time being) at the expense of the rest of the living community. Check out the discussion in the back of The Story of B or Hopfenberg & Pimentel's 2000 paper, Human Population Numbers as a Function of Food Supply. From their abstract:

That human population growth is itself a phenomenon with clearly identifiable ecological/biological causes has been overlooked. Here, human population growth is discussed as being subject to the same dynamic processes as the population growth of other species. Contrary to the widely held belief that food production must be increased to feed the growing population, experimental and correlational data indicate that human population growth varies as a function of food availability. By increasing food production for humans, at the expense of other species, the biologically determined effect has been, and continues to be, an increase in the human population. Understanding the relationship between food increases and population increases is proposed as a necessary first step in addressing this global problem.

I followed a link here from Ran Prieur's site where he makes the interesting point that:

[...] ecological laws do not say that growth must fit food supply. They say that growth is constrained by the lowest limiting factor. So a tree with plenty of sunlight can still be limited by lack of soil fertility or water. And humans with abundant food can still be limited by cultural factors. Paradoxically, one of the cultural factors that lowers human fertility is economic security, which can be created by abundant food.

My jury's out on this for the moment...

I'll say from the outset that I don't mean to deny the role of female emancipation and some of the other factors you cite here - clearly these have profound impacts on individual lives, affecting their everyday pragmatic decision-making. But I wonder if they ultimately play a secondary, symptomatic part in the broader ecological picture.

I'd be interested to hear your thoughts!


Jerah, I was right on track to have the 6 billionth - Eli was born a bit after, but close enough, so I sympathize.



A family starts by having two kids, besides there has always been an urge to splurge.