VKL: My name is Vinh-Kha. I recently turned 13 and am in the eighth grade. I participate in a program called QuEST, which provides to above-average performing students the opportunity to engage in creating projects of personal interest. This year, I am working on a paper on population growth tendencies and how they affect and are affected by the human development index and industrialization. Because of your professional background and expertise in projects on similar subjects, I think that your input would be very valuable. Could you please answer any or all the questions below? But please do not feel obligated to do so. Also, notice that I am working under this year’s district-wide theme: “Turning Points in History.”

What correlations are there between population growth and quality of living, measured by the HDI? What problems will these correlations cause?

PT: Human Development Index (HDI) has three components: life expectancy, education, and Gross National Income per capita. It’s one of the first attempts to get away from a purely economic view of quality of life (QOL). However, it still uses GNI per capita as a measure of the economic dimension of the QOL, which is not a good idea. It would be better to use real median income of a family, which is much less affected by changes in economic inequality.

There is a very complex relationship between population growth and HDI. First, the relationship is nonlinear – it is bad to have both too little population growth and too much of it. Too little, or even negative population growth results in population with too high proportion of elderly and too few people of working age. If it goes long enough, it may shrink the population below the point where there are positive returns to scale. What this means is that you need enough people for the society to function efficiently – enough people to train specialists for the many thousands of professions that are needed today, to give one example.

Population growth can also affect different parts of HDI in opposite ways. For example, if population grows faster than the economy can produce jobs, there will be too many people competing for a limited number of positions. Such competition can depress wages, so peoples incomes will suffer and that will affect their health. They will eat less vegetables and fruits, and many will not be able to afford health insurance. As a result, life expectancy will decline.

On the other hand, when competition for scarce jobs heats up, people will look for ways to get ahead of the pack. Getting a college degree is one way to increase one’s chances of landing a good job, so more people will enter college. This will result in more years of education, which will increase the HDI. However, such an increase will not reflect a real betterment of the quality of life.

As you can see, there is no simple answer to this question. Generally speaking, too rapid population growth will result in a decrease of average well-being. However, the HDI may not reflect such a decline, because it is a very imperfect measure of well-being.

VKL: Although industrialization has helped with the ability to have large populations within a small area and improved the human condition, what happens if or when population increases more so? How has industrialization been a turning point for urbanization?

PT: It was actually not industrialization, but a revolution in our food-producing capacity that resulted in increased population that could be supported from a given area. This did not necessarily increase popular well-being. When agriculture became very efficient, it did not need to employ as many people, and the ‘surplus’ workers had to move to cities in search of jobs. Premodern cities were very unhealthy places to live, and as a result average health declined. We can see it very vividly in the declining heights of Americans during the nineteenth century – they decreased by almost two inches, reflecting poor nutrition, greater disease, and lack of fresh air and sunlight.

VKL: Will population cap off and turn back down as in a sine wave? What evidence is there that this will happen?

PT: There can be no evidence for something that hasn’t happened yet. Future is unknown. However, it is highly unlikely that the global population will level off and stay at the same level indefinitely, as many projections suggest. It is unlikely for the simple reason that the number of people on Earth is a balance of deaths and births, and there is no reason to expect that births and deaths will balance perfectly. I see two scenarios. The most likely one is that the global population will decrease after reaching a peak. This has been the usual pattern in history – global population declined in the thirteenth century, then grew, declined in the seventeenth century, then grew, so it will probably decline in the twenty-first century (after which it will grow again). Another possibility is that something out of the realm of science fiction will happen – for example, we will start colonizing planets, or learn how to travel to other solar systems. Just because it is science fiction, it doesn’t mean that it is impossible, or even very unlikely. The nineteenth century French science fiction writer, Jules Verne, imagined many things that seemed fantastic at the time, but came to pass.

VKL: What is the future, population-wise and HDI-wise, of the human race? In what ways can a large population hurt or help a society? What are some examples of this? What types of cultures or social dynamics limit or otherwise affect population? When people are isolated, do they grow in numbers? What happens to populations when human development is low? What areas tend to have lower human development index? Why? What areas tend to have lower populations? Why?

PT: There are quite a lot of questions here, so let’s stay with the HDI and population. We have already discussed how population growth may have diverse effects on the HDI, although very rapid grow, exceeding the ability of the society to provide jobs for all new members is going to decrease the average level of well-being. It’s just that the HDI will not necessarily reflect it very well.

What about the feedback effect, how does the HDI affect population growth? What’s important to remember is that historical human populations tended to have very low HDIs, which did not prevent them from growing quite vigorously at times. I suppose we are again returning to the inadequacies of the HDI as an indicator of anything useful. Low HDI resulting from low education attainment, for example, may actually have a positive effect on population growth. At least, there is a very strong statistical correlation that the more years of education a woman has, the fewer babies she will give birth to.

VKL: Does your work relate to population growth tendencies? to my project? If so, how?

PT: I’ve done a lot of research on the interaction between population growth and political instability. Take a look at this article for a review:

http://cliodynamics.info/PDF/RevSEC.pdf

You also might read some papers on political demography by Jack Goldstone.

VKL: May I refer you to http://www.human.cornell.edu/pam/people/upload/Housing-Fertility-ReStat-Final-2.pdf? What do you think of the findings? Do you agree with them?

PT: A very interesting paper, whose results are in line with my intuition (meaning that I like them). However, I am not a specialist in this area so I cannot judge whether technically it is correct.

VKL: Population growth tendencies, though beneficial to our resources and advancement, will cause greater financial and societal separation between groups of people. Such separation can cause revolt and segregation within a community. What do you think of this as a possible thesis?

PT: What I think you are getting at is that population growth usually leads to greater inequality, especially economic inequality within a society. This is what we observe in historical societies. In our book with Sergey Nefedov, Secular Cycles, we show that sustained population growth results in a growing gap between the poor and the rich, what is sometimes known as the ‘Matthew Principle’ (the rich get richer, while the poor get poorer). In modern societies things are somewhat complicated. Later this week the online magazine Aeon will be publishing my article on the causes of inequality increases, as well as declines, in the United States over the last two centuries. I think that article will provide some additional answers to your questions.

VKL: To explain from information I have gathered, if people with higher financial income have lower fertility tendencies, then the rich population will shrink and the poor population will grow. This will cause a large gap between financial outputs. As people are more congregated in urban areas, this could have caused the Occupy-Wall-Street/1% scenario.

PT: It’s not clear at all that richer people have fewer children. Gregory Clark argued the opposite in his book, Farewell to the Alms (not that I wish to endorse his main message). In any case, read my forthcoming article in Aeon, where I present my view of why inequality increases and declines, and what consequences this has for political violence outbreaks.

Sincerely,
Vinh-Kha Le
Student of Sedgwick Middle School

Note: I received these questions from Vinh-Kha relayed by an e-mail from his teacher. I suggested that I respond to these questions on my blog, which was approved by Vihn-Kha’s parents and his teacher.