Demographics (MERLI)

Hey guys!

We would like to take this opportunity to once again thank Dr. Merli on her presentation and for giving us so much material to discuss! we wanted to recap on some key points drawn from the lecture.

History of population:

Dr. Merli presented an intriguing overview of demographics and its methodologies. She began her lecture with a historical overview of population growth. Since the emergence of organized societies, population growth has been tremendously slow. It was practically stationary until the mid-18th century. Once the industrial revolution began, population growth exploded exponentially. The population that had barely reached 1 billion people in 1750 has now grown to over 6 billion and is predicted to reach 9 billion in 2050 according to median UN estimates.

Demographic Transition:

The demographic transition refers to the cycle of birth and death rates that has occurred or is occurring in every society of the world. There are four stages. The first stage is high birth rates and mortality rates where the population has very little growth. This is the pre-industrial phase seen in Europe prior to the industrial.

In the second stage of the transition, mortality rates fall tremendously while fertility rates still remain high. These longer life spans can be attributed to better food supply and health care access.. This leads to tremendous population growth. Historically, this is observed in Europe and Western society during the early phases of the industrial revolution.

In the third stage of the demographic transition, mortality rates continue to fall while fertility rates also begin to decline. This is typically due to better education and economic opportunities for women, contraception access, and urbanization. Consequently, the population growth begins to level and is no longer rising as exponentially. This is seen in Western society in the later parts of the industrial revolution. Most of the developing world currently finds itself in this stage or in the second stage which explains their extraordinary population growth.

In the fourth stage of the demographic transition, both the mortality rates and birth rates are extremely low. Consequently, this leads to a steady, unchanging population. The US is an example of this. In some countries, the fertility rates can drop below the mortality rates leading to a declining population. This is currently observed in places like Italy and Japan. It should be important to note that these changes do not account for out migration or in migration and that those affect population changes as well.


Professor Merli’s expertise is on China’s implementation of public policy on fertility. In the 1960’s, the fertility rate in China was extremely high and averaged almost 6 children per women. Consequently, in the 1970’s, China initiated the “Later, Longer, Fewer” campaign to encourage the Chinese population to space out their births and have less children. The fertility rate sharply declined throughout the 1970’s to about 3 children per women. However, the “later, longer, fewer” campaign ultimately culminated in the “one-child policy” initiated in 1979. This restricts urban couples to only one child. As a result of this fertility control policy, the total fertility rate in present day China has fallen to 1.58. Since this is less than 2, this means the population is below replacement. *Replacement refers to the number of births required to “replace” the population. In basic terms for every couple that procreates, it would take two children to replace them. In reality replacement level is actually 2.1 instead of 2, as one needs to account for mortality.

The Future and Africa:

Interestingly, as population growth in Asia have begun to decline, growth in Africa has continued to grow exponentially. The African population has doubled since 1982. It is expected to rise to almost 4 billion by the end of the century. Nigeria is expected to be one of the most populated countries in the world. Thinking back to the demographic transition, Africa has experienced an increase in life expectancy and thus the mortality has declined. As with every country in the third stage of demographic transition, the fertility falls after the mortality does. Africa is currently in this stage.

Population Prediction:

The class ended with an enthusiastic discussion on the impact of high populations with respect to resources. Some were saying that population growth really doesn’t matter as much as the allocation of resources within the world. However, others emphasized that the population growth itself and the high volume of people will have the biggest burden. What does everyone think?

Cant wait for a rowdy discussion!

Christina Chao and Ryan Lion


11 thoughts on “Demographics (MERLI)

  1. Thanks for the interesting post, Christina and Ryann!

    One demographic statistic we learned in Dr. Merli’s class is the dependency ratio, which is the number of children and elderly people over the number of working-age people. A high dependency ratio indicates that a population has few workers supporting a large population. One of the consequences of China’s one-child policy is that it will lead to a high dependency ratio as the larger generations become older. While the one-child policy may be important for decreasing the total population, it will have to end at some point to bring the fertility rate back to replacement level. It should be interesting to see how much longer China sees this policy as beneficial and whether it becomes harmful at some point.

    Relating this to the discussion at the end of class, I began to wonder if it would be more helpful to try to encourage less consumption rather than limit population growth. If a country could come up with a policy to encourage its population to consume less resources overall without decreasing its population, it could maintain a healthy dependency ratio. I know there are obvious ethical and logistical considerations that must be addressed, but I was wondering what other people thought of this idea.

  2. Thanks Chistina and Ryan for your thoughtful posting!
    I would like to discuss more on the one child policy in China. Although it did slow down the increasing of population and have some positive impact on health care in China, it led to many other social problems in China. As Dominic discussed above, the dependency ratio in China is high. As the first generation of only-children came of age for becoming parents themselves, the single-child generation suffers great burden from their families since they have to provide support for their two parents and four grandparents. This “1-2-4 problem” leaves the older generation with increased dependency on the social retirement funds and system and lead the community have to bear more burden as well. In response to such issue, the one-child-policy is more flex nowadays and government have decided that couples are allowed to have two children if both parents were only children themselves.

    Another social problem that resulted from one-child policy is the loss-of-single-child family, which refers to the single child in their family died and the parents are too old to have additional children after the loss of the single child. The number of loss-of-single child family is increasing 76000 every year and is projected to reach to 10 million. According to a survey, most of the parents of the loss-of-single-child family are suffering from economic difficulty and are living on a basic living allowances. They are also more likely to suffer from different degrees of depression and chronic diseases. But these group of vulnerable people did not get enough attention.

    I am also curious on the mobile population in the community. In China, a great amount of working-age people are moving from rural area to big cities for better job opportunities but they cannot get high quality health care system because the urban health insurance system is different from the rural one. In addition, since they are not well educated, they can only do the job with high risk of injury and always suffer more diseases. Studies on this population is difficult since they always move and have no stable job. Do you have any thoughts on how to recruit and follow-up these cohort in a research? Do you think mHealth is a possible solution for this?

    • Thanks Enying! Wonderful thinking!

      I do think mHealth can be a reasonable solution to this issue. In addition, I think strengthening the regulation and management of this kind of migrant population is also of critical importance currently.
      Specialized agency in charge of the management of the migrant population should be established. The management measures should be improved, and migrants file management system and identity verification should be well implemented to fully grasp the population information.

    • Enying,

      Thanks for such a thoughtful post! I agree that in terms of straight demographics, China’s one-child policy has been incredibly effective and successful. However, I think a major challenge of thinking about the policy in isolation (pure demographic numbers), is that it ignores many of the other implications. The one-child policy has had huge cultural implications on the Chinese policy that are incredibly far-reaching. The policy has very deferentially effected those living in urban and rural settings, men and women, and has created a huge generational gap.

      One major example that you mentioned in your post is the “1-2-4” problem and the social pressures that are now placed on the current generation. Another is the female suicide rate in China, now the highest in the world and three times higher than the male suicide rate. Many women have had to undergo horrific abortions (some “optional” and others decidedly not) and decide whether to keep their daughter or continue trying for a son. Many women growing up in the current generation have to deal with familial feelings of resentment over their gender as well as the added social pressure to be successful and eventually provide for their families.

      There are so many cultural problems that have resulted from this policy that it is often hard to tell what the true cost-benefit of the policy was. What do you all think ultimately matters? Do pure population numbers matter more than some of the cultural implications that may be the fallout of such policies?

  3. It was unfortunate that at the end of class we weren’t able to have a full discussion on this topic. From Dr. Merli’s position it seemed that she was supporting the idea that increasing population size isn’t the problem, and that the real problem is consumption. In class I didn’t disagree with her point about consumption. It is true that consumption patterns are a major driver in the depletion of resources for all. On the other hand it seems short sighted to say that population size has no contribution to this issue. The figures and ideas supporting my claim come straight from Dr. Merli’s slideshow itself. First off, our current population level has increased exponentially in the last century. The population doubling rate is such that the population is now able to double faster than it ever has before. This fact along with our increased ability to keep people alive with medical advancements means that the world’s population is an idea that must be thought about. This overwhelming population growth in the current century places new burdens on the limited supplies of resources in the world to sustain the population. Second, most of this growth is shown to be in the developing countries where medical advancements are catching up to those of the developed world. That paired with the higher fertility rates sets the stage for the population boom that will occur in these areas, as Dr. Merli spoke of in her presentation.

    Now lets get to the idea of consumption. It is without a doubt a major issue to discuss when the variables in play are total world population and world resources. The population’s consumption of the limited goods is important. In places like the US our consumption patterns are far from the basic necessities to sustain life. We consume far beyond our means and that means that we consume at a level that can’t be sustainable across the globe. This idea is now being propagated across the globe, and we have touched upon this issue in other classes. The idea of urbanization and globalization bring with it changing consumption patterns of the places that they impact. This is turn increases the average consumption worldwide. Now if we are changing the consumption patterns in places with high fertility rates and increasing population sizes then there will be a shortage of resources for the rest of the globe. This fact makes it impossible to say that population isn’t the issue. I would concede that if we didn’t allow for globalization to increase the consumption patterns then we might be talking about this issue a bit differently. Even in that setting of unchanging consumption patterns, if we increase the total population of people consuming then the overall resource supply is still going to decrease.

    I think a simple way to think about this issue is to think of two different groups with one group having a consumption pattern of 5 and the other group having a consumption pattern of 1. Furthermore, the resources are limited and the total resources amount to 1000. Finally, there are 10 people in the high consumption group and 100 people in the low consumption group. In this setting the high consumption group consumes 50 of the total resources, while the low consumption group consumes 100 of the total resources. This scenario leaves us with 850 total resources left. Now lets increase the number of people in the low consumption group without increasing their consumption level. Let’s just give this group a total of 250 people which amounts to 250 of the total consumption. This now leaves us with 700 of the total resources left. This example illustrates only population change and not consumption pattern changes, and still there is an issue of limited resources. Now lets factor in the reality that consumption patterns if unchecked will increase the patterns in the low consumption group. Lets just call it 3. When you redo the calculations this way with the increased population size the consumption equals 750, and leaves a grand total of 200 total resources left. Although this is a very simplistic way to think about it, this example shows that population size does contribute to decreasing resourcing regardless of the consumption level.

    If there is an argument to refute what I am proposing please tell me. I am not sure how it is possible to say with a straight face that population size has no impact on resources. There must be a tipping point, the world can’t sustain a trillion people can it?

    • Hey Tony,

      You definitely bring up a valid concern that the earth cannot support a growing population indefinitely however I think where your frustration is occurring is in the measures we are using to talk about this issue. I’m in Dr. Merli’s Demographics class this semester and just wanted to remind everyone that demographics is a science and math and doesn’t take opinion into the calculations. So when we project the population into the future using demographics, we only consider birth and deaths rates, not land space or resource capacity.

      Maybe sustainability should factor into the equation for population projection, however, currently fertility and mortality rates are the only assumptions demographers use in population prediction.

    • Something that wasn’t really brought up in the discussion was how technology can temper the effects of population growth on resource availability. The Green revolution in the 1940s and 1960s brought a variety of technological advances and tech. transfers to the developing world that increased the yield of agriculture. For example, Normal Borlaug was able to genetically modify wheat to create dwarf wheat which had both higher disease resistance, a longer life span, and higher grain yield.

      If we take technological advances in resource availability (Maybe someone can comment on water?) Dr. Merli’s argument makes a little more sense. As long as technology can allow resource availability to keep pace with population, the only other important factor is limiting consumption.

      Anyways, thats my take. I’d love to hear some feedback.

  4. Hey everyone, just wanted to share a New York Times op-ed piece written by one of Dr. Merli’s colleagues about the relaxing of China’s One-Child Policy (which Dominic mentioned above), touching on the political implications of the decision. China announced last week that it would allow both urban and rural couples in which just one parent is an only child to have up to two children. How much of an effect do you think the easing of this policy will have on the birth rate in China? I personally am skeptical about how much of an effect it would have (see the article authored by Dr. Merli that I’ve also included below).

    Link to op-ed piece:
    Link to Merli’s article (Note: I found this via the Duke Libraries website, so you’ll probably have log in with your NetID to see it):

  5. Hi Everyone,

    I completely agree with Tony, and the growing population is often something I think about going into global health. Is it unethical to not provide someone treatment for their illness, or is it unethical to provide everyone treatment and let the population get so large that the stability of our environment collapses?

    Eeshan, you have a point with the technological aspect. This can be used to increase production, but we have to think about the effects of changing the chemical structure of our food. The rising levels of celiacs disease, gluten intolerance, and diabetes indicate that this alternative wheat source may not be the best thing for our population’s health or nutrition.

    With population growth and increased wealth comes the unnecessary demand for more nutrition sources for consumption and energy sources for power. Commercial farms, and natural resource extraction companies respond to this demand, and destroy the production ability of large amounts of land. Monoculture agriculture depletes soil of crucial nutrients needed to grow produce, and natural gas extraction by fracking uses millions of gallons of groundwater, a precious resource in places like Texas, where towns have recently run dry for days at a time.

    At the same time, policies like China’s one-child-policy have huge cultural impacts that can’t yet be fully visualized. It seems the most likely form of population control will come from uncontrollable forces such as a highly pathogenic infectious disease pandemic, or the increasing frequency of adverse weather events.


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