Now that you are familiar with some basic demographic concepts, we can discuss population growth and decline in more detail. Three of the factors just discussed determine changes in population size: fertility (crude birth rate), mortality (crude death rate), and net migration. The natural growth rate is simply the difference between the crude birth rate and the crude death rate. The U.S. natural growth rate is about 0.4% (or 4 per 1,000 people) per year (Rosenberg, 2009). When immigration is also considered, the total population growth rate has been almost .7% per year (Population Reference Bureau, 2017).

Population Growth

Figure 8.9 “International Annual Population Growth Rates (%), 2005–2010” depicts the annual population growth rate (including both natural growth and net migration) of all the nations in the world. Note that several African nations are growing by at least 3% per year or more, while most European nations are growing by much less than 1% or are even losing population, as discussed earlier. Overall, the world population is growing by over 80 million people annually.

Figure 8.9 International Annual Population Growth Rates (%), 2005–2010

Source: Adapted from http://en.wikipedia.org/wiki/File:Population_growth_rate_world_2005-2010_UN.PNG.

To determine how long it takes for a nation to double its population size, divide the number 70 by its population growth rate. For example, if a nation has an annual growth rate of 3%, it takes about 23.3 years (70 ÷ 3) for that nation’s population size to double. As you can see from the map Figure 8.9 above, several nations will see their population size double in this time span if their annual growth continues at its present rate. For these nations, population growth will be a serious problem if food and other resources are not adequate or adequately distributed.

Demographers use their knowledge of fertility, mortality, and migration trends to make predictions about population growth and decline several decades into the future. Coupled with our knowledge of past population sizes, these projections allow us to understand population trends over many generations. One clear pattern emerges from the study of population growth. In the earliest forms of society, when societies were small, population growth was slow because there were relatively few adults to procreate. Additionally, death rates were high, which helped to neutralize high fertility rates within these societies. But as the number of people grows over time, so does the number of adults. More and more procreation thus occurs every single generation, and population growth then soars.

We see evidence of this pattern when we look at world population growth. When agricultural societies developed some 12,000 years ago, only about 8 million people occupied the planet. This number had reached about 300 million about 2,100 years ago, and by the 15th century it was still only about 500 million. It finally reached 1 billion by about 1850 and by 1950, only a century later, had doubled to 2 billion. Just 70 years later, it more than tripled to 7.6 billion, and it is projected to reach more than 9 billion by 2050 (U.S. Census Bureau, 2010) (see Figure 8.10 “Total World Population, 1950–2050”).

Figure 8.10 Total World Population, 1950–2050

Source: Data from Source: U.S. Census Bureau, International Data Base. “Total Midyear Population for the World: 1950-2050”, published 10 May 2000; http://www.census.gov/ipc/www/

Eventually, however, population growth begins to level off after increasing rapidly, as explained by demographic transition theory, discussed later. We see this in the bottom half of Figure 8.10 “Total World Population, 1950–2050,” which shows the average annual growth rate for the world’s population. This rate has declined over the last few decades and is projected to further decline over the next four decades. This means that while the world’s population will continue to grow during the foreseeable future, it will grow by a smaller rate as time goes by, and may eventually reach a peak, after which it may stabilize and then start to decline. The growth that does occur will be concentrated in the poor nations in Africa and some other parts of the world. Still, even there the average number of children a woman has in her lifetime dropped from six a generation ago to about three today (a very rapid decrease within one generation).

Theories of Population Growth

The numbers just discussed show that the size of the world population has increased tremendously in just a few centuries. Not surprisingly, people have worried about population growth and specifically overpopulation at least since the 18th century. One of the first to warn about population growth was Thomas Malthus (1766–1834), an English economist, who said that population increases geometrically (2, 4, 8, 16, 32, 64, 128, 256, 512, 1024…). If you expand this list of numbers, you will see that they soon become overwhelmingly large in just a few more generations. In contrast, Malthus (1798/1926) said that food production increases only arithmetically (1, 2, 3, 4, 5, 6…) and thus could not hope to keep up with the population increase, and he predicted that mass starvation would be the dire result. This theory is referred to as the Malthusian Theory.

Thomas Malthus, an English economist, wrote that population increases geometrically while food production increases only arithmetically. These understandings led him to predict mass starvation. Wikimedia Commons – public domain.

During the 1970s, concern about population growth increased again, leading to a call by some activists for zero population growth (ZPG). There was much concern over the rapidly growing population in the United States and around the world, and there was fear that our “small planet” could not support massive increases in the number of people (Ehrlich, 1969). Some of the direst predictions of the time warned of serious food shortages by the end of the century.

Fortunately, Malthus and ZPG advocates were wrong to some degree. Although population levels have certainly increased, the projections in Figure 8.10 “Total World Population, 1950–2050” show that the rate of increase is slowing. Among other factors, the development of more effective contraception, especially the birth control pill, has limited population growth in the industrial and post-industrial nations and, increasingly, in lower-income nations. Food production has also increased by a much greater amount than Malthus and ZPG advocates predicted. Concern about overpopulation has weakened, as the world’s resources seem to be standing up to population growth. Widespread hunger in Africa and other regions does exist, with hundreds of millions of people suffering from hunger and malnutrition, but many experts attribute this problem not to overpopulation and lack of food but rather to problems in distributing the sufficient amount of food that exists.

Another factor might have played a role in weakening advocacy for ZPG: criticism by people of color that ZPG was directed largely at their ranks and smacked of racism. The call for population control, they said, was a disguised call for controlling the growth of their own populations and thus reducing their influence (Kuumba, 1993).

Demographic Transition Theory

An alternative theory on population growth subscribed to by most sociologists is the demographic transition theory. This theory links population growth to the level of technological development across 5 stages of social evolution. As seen below in Figure 8.11 “Demographic Transition Model,” In the first stage, coinciding with preindustrial societies, birth rate and death rate are both high. The birth rate is high because of the lack of contraception and the several other reasons cited earlier for high fertility rates, and the death rate is high because of disease, poor nutrition, lack of modern medicine, and other problems. These two high rates cancel each other out, and little population growth occurs.

In the second stage, coinciding with the development of early industrial societies, the birth rate remains fairly high, owing to the lack of contraception and a continuing belief in the value of large families, but the death rate drops because of several factors, including increased food production, better sanitation, and improved medicine. Because the birth rate remains high but the death rate drops, population growth takes off dramatically.

Figure 8.11 Demographic Transition Model

Source: Adapted from https://commons.wikimedia.org/wiki/Category:Demographic_transition#/media/File:Demographic-TransitionOWID.png CC BY-SA 4.0

In the third stage, as industrial societies mature, the death rate remains low and the birth rate finally drops as families begin to realize that large numbers of children in an industrial economy are more of a burden than an asset. Another reason for the drop is the availability of effective contraception. As a result, population growth slows, and, as we saw earlier, it has become quite low or even gone into a decline in numerous mature industrial middle-income nations.

Stages 4 and 5 demonstrate the demographic trends in post-industrial societies, where the birth rate falls to low levels on the same par as death rates, and in some cases, as shown in Stage 5, nations begin to experience natural decrease in their populations as birth rates fall below death rates. Demographic transition theory, then, gives us more reason to be cautiously optimistic regarding the concerns associated with overpopulation: as poor nations industrialize, their population growth rates should start to decline.

Population Decline and Pronatalism

Still another reason for the reduced concern over population growth is that birth rates in many post-industrial nations have slowed considerably. Some nations are even experiencing population declines, while many more are projected to have population declines by 2050 (Goldstein, Sobotka, & Jasilioniene, 2009). As discussed, for a country to maintain its population, the average woman needs to have 2.1 children (not accounting for immigration). Post-industrial nations, as well as many industrial nations, are far below this level. Increased birth control is one reason for their lower fertility rates but so are decisions by women to stay in school longer, to go to work right after their schooling ends, and to not have their first child until somewhat later.

Ironically, these nations’ population declines have begun to concern demographers and policymakers (Shorto, 2008). Because people in many industrial nations are living longer while the birth rate drops, these nations are increasingly having a greater proportion of older people and a smaller proportion of younger people. As this trend continues, it will become increasingly difficult to take care of the health and income needs of so many older persons, and there may be too few younger people to fill the many jobs and provide the many services that post-industrial society demands. The smaller labor force may also mean that governments will have fewer income tax dollars to provide these services.

To deal with these problems, some governments have initiated pronatalist policies aimed at encouraging women to have more children. In particular, they provide generous child-care subsidies, tax incentives, and flexible work schedules designed to make it easier to bear and raise children, and some even provide couples cash payments when they have an additional child. For example, Russia in some cases provides the equivalent of about $9,000 for each child beyond the first, while Spain provides 2500 Euros (equivalent to about $3,400) for each child (Haub, 2009).

Spain is one of several European nations that have been experiencing a population decline because of lower birth rates. Spain has adopted pronatalist policies to encourage people to have more children. Photo by Tomás Malco Malík from Pexels.

Population Pyramids

As discussed, fertility, mortality, and migration rates are used to examine the current state and future projections for a given population. In addition to these figures, the study of population also includes review of the age and sex composition of societies. In fact, the demographic changes outlined in the demographic transition theory are also reflected in the age and sex composition of societies. Parallel to Figure 8.11 “Demographic Transition Model” we can lay out and compare age-sex graphs (known as population pyramids) to better understand the demographic transitions that societies undergo. As demonstrated below in Figure 8.12 “Population Pyramid, Vietnam, 2016,” population pyramids graphically represent the population of a society by sex, in 5-year age increments.

Figure 8.12 Population Pyramid, Vietnam, 2016

Source: Adapted from https://commons.wikimedia.org/wiki/File:Population_pyramid_of_Vietnam_ 2016.png#/media/File:Population_pyramid_of_Vietnam_2016.png Wikimedia Commons — Public Domain

Population pyramids depict the male portion of a society on the left (in blue) and the female portion of a society on the right (in pink). Each horizontal bar represents a 5-year age group. At the base are people ages 0-4, the next horizontal bar are people ages 5-9 and so on up the chart until you get to people who are 100+ years old. Looking at the example of Vietnam, this means that there are just under 4 million boys aged 0 – 4, while there are roughly 3.5 million girls in this same age group. While it is natural for more boys to be born than girls (about 105 boys per every 100 girls), the gap of 500,000 million more boys than girls in the 0-4 age group in Vietnam is significant and demonstrates a preference for boy babies. Technologies such as amniocentesis and ultrasound can be used to determine fetal sex, prompting the decision to terminate a pregnancy if the fetus is found to be female. Another factor that stands out in Vietnam’s population pyramid is that in the last 20 years, Vietnam’s population growth seems to have stabilized, with very similar numbers of males and females aged 0-4, 5-9, 10-14 and 15-19. As we will discuss below, this may reflect Vietnam undergoing rapid industrialization.

The shape of population pyramids reflects the stage of a country’s demographic transition, as shown below in Figure 8.13 “Population Pyramids and the Demographic Transition Model.” A country in the first stage of the demographic transition, as discussed, will have both high birth and death rates, evidenced by a population pyramid with a wide base (lots of children due to a high birth rate) and concave sides, reflecting high rates of death in each age group. Such a shape would typically show that a country, having high birth and death rates, is pre-industrial. There are exceptions, though. Some countries that have been war-torn for prolonged periods of time may take on this shape as well, providing that they have a high birth rate.

Figure 8.13 Population Pyramids and the Demographic Transition Model

Source: Adapted from User:SuzanneKn – http://en.wikipedia.org/wiki/Image:Dtm_pyramids.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3411959 Wikimedia Commons — Public Domain

As a society starts to industrialize and transition to Stage 2 of the demographic transition, its population pyramid begins to change shape. It retains its wide base due to continued high fertility, but the shape becomes more an equilateral triangle, reflecting a declining death rate. Today, mostly low-income nations and some low-middle-income nations take this shape. Figure 8.14 “Population Pyramid, Papua New Guinea, 2017” below nicely demonstrates this shape.

Figure 8.14: Population Pyramid, Papua New Guinea, 2017

Source: Adapted from https://commons.wikimedia.org/wiki/File:Papua_New_Guineapop.svg Creative Commons CC0 1.0 Universal Public Domain Dedication.

As illustrated in Figure 8.13, “Population Pyramids and the Demographic Transition Model,” population pyramids reflecting the third stage of the demographic transition begin to take on a haystack shape, reflecting low mortality and falling birth rates. This haystack shape shows fertility is reaching replacement level, and that more people are living to old age, as demonstrated by Iceland’s population pyramid below in Figure 8.15 “Population Pyramid, Iceland, 2016.”.

Figure 8.15: Population Pyramid, Iceland, 2016

Source: Adapted from https://commons.wikimedia.org/wiki/Category:Population_pyramids_of_Iceland#/media/File: Population_pyramid_of_Iceland_2016.png Wikimedia Commons — Public Domain

Finally, the population pyramid for stage 4 of the demographic transition is depicted in Figure 8.13 “Population Pyramids and the Demographic Transition Model” above, and shows the similar haystack shape of stage 3, however, the pyramid narrows at the base indicating that birth and death rates are both low and that birth rate is starting to dip below death rate. This shape characterizes most high-income nations.

Population pyramids contain other information beyond the stage of the demographic transition of a nation. As noted earlier in our discussion of Vietnam’s population pyramid, we can see sex imbalances demonstrated, reflecting preference for male offspring. It is more common to see a sex imbalance at the top of a population pyramid, since women almost universally live longer than men, however, a sex imbalance favoring females at other points in a population pyramid may demonstrate that there was a war in which many men died or a prolonged period of mass emigration of males. Similarly, it is not unusual for societies to have periods of baby booms, which will show as a bulge in a population pyramid. Similarly, if a society experiences a severe natural disaster or health crisis, such as the high rate of HIV and AIDS found in a number of southern African nations, the resultant increase in the mortality rate will be visible in their population pyramid.

 

Key Terms

Demographic Transition Theory – A theory on population growth that demonstrates trends in birth and death rates over time, showing a correlation between population growth and form of society, and which predicts that with industrialization, population growth naturally slows and eventually declines.

Malthusian Theory – A theory by Thomas Malthus on population growth that promotes the idea that population growth increases exponentially and increase in food production occurs arithmetically, resulting in a growing gap between the size of the population and the ability to produce enough food to feed this population. The consequences predicted to result from this gap are mass starvation and conflict over increasingly scarce resources.

Natural Growth Rate – the difference between the crude birth rate and the crude death rate.

Population Pyramid – a graphic representation of the age and sex structure of a given society.

Pronatalism Policies – Policies aimed at encouraging women to have more children.

Zero Population Growth – A neo-Malthusian theory that espoused the idea that population growth will outstrip food resources as well as non-renewable resources, prompting the call for reduction in fertility.