Population

 The Big Idea: The human population of planet earth is growing. In November of 2022 the planetary population reached 8 billion people. It had hit 7 billion in 2011 and 6 billion in 1999. In 2037 or thereabouts, the population will probably reach 9 billion, at which point it will have—hopefully—leveled out.

This growth has not been evenly distributed. Industrialized and economically developed countries are experiencing, in many cases, population decline—every year, more people die in countries like South Korea and Japan than are born. Meanwhile, the globe’s least developed countries continue to experience sustained population growth. And, urban areas are experiencing population increases, not because urban women are having more children (they tend to have fewer), but because people from rural areas are moving to the cities in search of greater opportunities.

Every ten years, the United States Census Bureau makes a count of all of the people living in the United States, and continues to make estimates throughout the intervening decade. In 2020, that number was approximately 331.4 million, an increase of 22.7 million from the 2010 census. Such census taking takes place in almost every country on earth and reveals the unevenness of the planet’s population change.

As of June 27, 2023, the People’s Republic of China’s Population stood at 1.455 billion, a decline of about 850 million from the year before.. As China’s economy has boomed over the last few decades, young women have become increasingly reluctant to have children. As a result, China’s aging population saw more deaths (10.4 million) than births (9.56 million). China, like many of the world’s most industrialized and developed countries, has been experiencing negative population growth. (South China Morning Post).

But numbers, even very large numbers, do not tell us everything. In order to decide where to build new schools, boards of education need to know where young families are making their homes. Executives at McDonalds and every other restaurant chain need to know where people live and work, and where they drive, and how much money they have to spend. Schools, businesses, hospitals, governments and religious institutions need population data to make decisions and plan for the future.

The Census Bureau provides massive amounts of this kind of data to anyone willing to spend time analyzing it.

Sometimes, in order to make data useful, we need to put it into a format we can see—kind of like a map for numbers. In population studies, one of the most useful way to visualize data is with a Population Pyramid:  a graphical illustration that shows the distribution of age groups, divided by sex, in a country or region.

The population pyramid above represents the population of the world in 2022. The vertical axis represents age cohorts (that is, groups of people born at about the same time) from birth to very old age. The horizontal axis represents the percentage of the total population represented by that cohort. Notice that the zero is in the middle. This is because the bars of the graph are divided among males and females with the females on the right (with red bars) and the males on the left (with blue bars). So, this population pyramid tells us that, in 2022, 4.3 percent of the total population was made up of baby boys under the age of four, while 4.0 percent was made up of baby girls. A little math tells us that this cohort was born between the years 2019 and 2022 and that they will start school between the years 2025-2030 and will begin graduating from high school around 2037. Many of the girls will have become young women and start having children beginning in 2037 (if not earlier) and continue for another twenty years. As young men and young women, they will start to work around 2037 and continue to earn a living until the 2080s. By the year 2100, most will have died, though a few can be expected to continue living into the Twenty-second century.

If you noticed that baby boys outnumbered baby girls, you are on to something important. Baby boys almost always outnumber baby girls, and males continue to outnumber females until age 40. Whenever there is an exception to this, it is because society has intervened to prevent the birth of girls. This happened in China during that country’s “One Child Policy” when government policy strongly encouraged families to stop having children after the birth of the first child and Chinese tradition placed a high value on that one child being a boy.

Between age 40 and 55, a time we might call “middle age,” the numbers of males and females become very nearly the same. Then, inexorably, males begin to die at slightly higher rates than females. The very top of the pyramid belongs almost entirely to elderly women.

Not all population pyramids look like this.

In 2019, Romania’s population of almost 20 million people looked like anything but a pyramid. It tells us that the numbers of births have been falling since the 1970s, and there was a sudden drop in the numbers of children born during the late 1950s. We might also notice that, among older adults today, women substantially outnumber men.

What this population pyramid does not tell us is why the population of Romania seems to have behaved so strangely during the last century. Here is where we need to know the history of this lovely country. Romania was on the losing side of the Second World War, which might account for the loss of men now in their nineties. From the late 1940s through the end of the 1980s, Romania was ruled by a series of brutal and remarkably incompetent communist dictators. In the 1980s, food became scarce and healthcare was hard to find. Adults died younger than they might have and had fewer children. Even after the overthrow of communism in Romania, it took the country a long time to begin to recover economically. Many Romanians, able to travel freely for the first time, moved to Western Europe to look for work. All of these events and others (including the popularity among Western European and Americans of adopting Romanian children in the 1990s) left their marks on the population pyramid.

The Population Pyramid for the United States is much more stable than that of Romania, though it too reflects a slowly declining number of births over the last thirty years. This pyramid tells its own story.

During the early decades of the 20th century, American families tended to be large. The Great Depression (1929-1939) caused a decline in childbirths since people who are unsure where their next meal is coming from tend to be reluctant to have children. The Second World War also reduced fertility rates, since millions of young men were off fighting in Europe or the Pacific rather than at home starting families. When the War was over, and the soldiers started coming home, finding jobs and getting married, the numbers of births, predictably, boomed. From 1946 until 1972, American families grew large again. So many children were born in this period they came to be called Baby Boomers.  In the mid-1970s, however, as the Baby Boomers entered their prime child bearing and child rearing years, female boomers started finding other things to do with their lives than having babies. They went to school for longer than their mothers, married later, and had fewer children.  It is perhaps not a coincidence that the birth control pill (known at the time simply as “The Pill”) and other reliable forms of contraception were introduced in the 1960s, so that becoming pregnant became more of a choice and less of a gamble.  Many industrialized countries experienced the same phenomenon:  high birth rates in the decades after World War II followed by a decline starting in the 1970s.

This had a significant and unexpected consequence.  Although there were, and are, many very good reasons to aim for a population growth rate of zero (and we will be exploring those reasons later in this lesson), the short term consequences of lower population growth rates have proven to be substantial.  (And will be discussed a few paragraphs down the page.)

Still, the consequences of maintaining a high rates of population growth with big families can be far more troubling. Consider the population pyramid for Nigeria.

Nigerian women have, on average, 4.72 children over their lifetimes. The population is growing at a rate of 2.6 percent per year. By contrast, women in the United States have, on average, 1.84 children. If Nigeria’s population growth rate continues at its current rate, it could be expected to double in about 30 years to 400 million people. Nigeria is a fertile and industrious country, but it does not have infinite resources. Continued population growth will almost certainly lead to higher rates of poverty, malnutrition, and infant mortality.

Americans tend to shake their heads in dismay at such large rates of child bearing and population growth. In industrialized countries, like the United States, Japan, and Western Europe, parents expect that the one or two children that they do have will almost certainly grow to adulthood. Parents in these industrialized countries also count on the social safety systems of their home countries to provide old age pensions and health care as they grow older. Children may be welcome additions to the family, but they are expensive and are rarely expected to provide for mom and dad as the parents grow old. In less developed countries, rates of childhood death are often much higher and families are expected to play a much larger role in caring for aging parents. If parents hope to avoid poverty in their old age, they are going to need at least a couple of surviving children helping to support them.

In Most Developed Countries, children are thought of as economic liabilities. Though they may be sources of joy, they are also expenses that must be borne for a couple of decades before finally becoming independent.

In Less Developed Countries, children are viewed as economic assets. Children can help with the labor when they are young, and as they grow older, they can begin to take over family responsibilities, including the care of elderly parents. While this is absolutely true, a growing population eventually runs into the limitations of resources that, by definition, less developed countries confront.

Declining birth rates in Economically Developed countries also create problems, at least in the short term. Children require a lot of care and attention from adults.  Not only do adults have to provide food, care, clothes, housing, and X-Boxes for the kids, they have to teach them the skills they will need as adults.  Adults don’t mind providing this attention to the needs of children, in part because they have faith that, when today’s adults become too old to work and need help themselves, today’s kids will have grown into working adults and will be there to pay back the debt—providing social security, nursing homes, and all the things elderly adults need. As long as the population of working adults outnumbers the elderly population, the system works.  Working adults (ages 20 to 65) can support their children as well as a much smaller number of retired adults who (until relatively recently) had the good grace to die around the age of 68. 

However, in the 1970s, Americans, Europeans, and members of other developed regions began to live healthier and longer lives and to have fewer children. This set up this Baby Boomer cohort for problems when they stopped working.  Fewer births in the 1970s and beyond meant that, beginning in the 1990s, there would be fewer working adults to pay for all the things retired people would need to be able to enjoy their retirement.  The Population Pyramid was no longer a pyramid.  It had developed bulge near the top.  That bulge represents a larger population of older population relative to the working population. Since older people eventually retire from working, they come to depend on the labor of working age adults to meet their needs. The number of dependent people (older adults and young children) divided by the number of working adults is called the Dependency Ratio.

The Dependency Ratio  (DR) is calculated by dividing the total number of dependents (adults 65 years of age or older plus the number of children aged 14 or younger)  by the total number of adults aged 15-64.  

All Dependents/Working Adults X 100 = DR

In the United States, there are 112.9 million dependents supported by 214.2 million working age adults. Putting that into our Dependency Ratio Equation, we get

112.9 / 214.2 X 100 = 52.7

This means that, for every 100 people of working age, there are 52.7 retired adults and children under 14. The larger the ratio, the fewer people each working adult has to support. As the number becomes smaller, the burden on working adults becomes greater.

As today’s workers have fewer children, and as adults expect to live longer, future generations of working adults (such as the one’s now in high school) can expect to pay a larger percentage of their income into social security and other taxes to support the elderly.

For more information on the Dependency Ratio and what it can mean (and alternate ways to calculate it), go to “Dependency Ratio and How it Affects You.”

Other countries with aging populations and growing dependency ratios are Japan, China, and much of Western Europe.  

China represents a special case. For most of its long history, China had been an agrarian, village based society.  Family-owned farms required a great deal of work, and every additional birth—especially of a son—was celebrated because it added to the wealth of the family.  This attitude towards large families continued, even as China’s total population climbed toward one billion people and as more and more people lived in cities and worked in factories.  Eventually, if this population growth continued, China would face massive over-population and starvation.

In the late-1970s, therefore, the Chinese government instituted a One-Child Policy.  Quite simply, families were required to limit themselves to one child. This policy resulted in a dramatic decrease in China’s birth rate, although the population continued to increase.  Because of the great unpopularity of the One Child Policy, and because of the burdens placed on working adults by the dependency ratio, it was changed to a Two-Child policy in 2016.  Still, as of this writing, in 2023, China’s population has begun to decline and is likely to fall below that of India for the first time.

Demographic Concepts: When we think about population, there are several basic concepts that help us understand what a population is doing. For the most part, populations are driven by three events: children being born, people dying, and people moving from one place to another.

Populations are either growing, declining or remaining steady. For this discussion, we are going to ignore the impact of migration (people moving into or away from a region) and focus instead on births and deaths. When a population is growing, the number of births in a given period of time (usually a year) exceeds the numbers deaths. More people are born than die. When a population is stable, the two numbers are close to the same and when a population is in decline, more people die in a given year than are born.

If we created a very small country with a population of 1000 people in the year 2000, and the population increased by 10 in the first year, then we would report a population growth of 1% (1000/10) X 100. If the population continued to grow by 1 percent during the second year, the population would increase to1021

Crude Birth Rate:  The number of live births occurring among the population of a given geographical area during a given year per 1000 population.

Total number of Live Births/Total Population X 1000 =  Crude Birth Rate

This calculation is “crude” because it is easy but ignores a lot of important information: The denominator in this equation is the total population, but of course only women between the ages of 15 to 40 are going to have children. Still, by comparing the crude birth rates of a region over time tells us a lot about what is happening to the population.

Crude Death Rate:  The number of deaths occurring within a population of a given geographical region during a given year per 100,000 population.

Total Deaths / Total Population  X 100,000 = Crude Death Rate.

The Natural Rate of Increase is the difference between the number of births in a region in a year and the number of deaths in the same region per 1000.

Natural Rate of Increase = (Number of Births — Number of Deaths) X 1000. In some regions, the NRI is a negative number, indicating that the population is falling. In the United States, the low NRI is offset by immigration—people moving into the country from other regions.

For some useful background information on these demographic concepts see:

https://www-doh.state.nj.us/doh-shad/view/sharedstatic/CrudeDeathRate.pdf

https://courses.lumenlearning.com/boundless-sociology/chapter/population-dynamics/

Overpopulation:  When the population of a species exceeds the carrying capacity of its ecological niche.  

More Essential Concepts:

Factors that influence distribution of human populations at different scales:

Climate, landforms, culture, economics, history, politics

Population Density/relevance: arithmetic, physiological, agricultural

Consequences of Population Distribution

Political, economic, social processes (including social services)

Carrying Capacity

Population Composition

Age Structure

Sex Ratios

Population Pyramids

Population Dynamics

Fertility

Mortality

Migration

Natural Increase

Doubling Time

Social, cultural, political, and economic factors influencing fertility, mortality, and migration rates.

Demographic Transition Model

Epidemiological Transition Model

Malthusian Theory

Population Policies

Pro-natalist policies

Anti-natalist policies

Immigration Policies

Women and Demographic Change

Ravenstein’s Laws

Changing patterns of work, mortality, migration, education, fertility

Aging Populations

Dependency Ratio