Between 2011 and 2012, we reached a population milestone of 7 billion humans on the earth’s surface. The rapidity with which this happened demonstrated an exponential increase from the time it took to grow from 5 billion to 6 billion people. In short, the planet is filling up. How quickly will we go from 7 billion to 8 billion? How will that population be distributed? Where is population the highest? Where is it slowing down? Where will people live? To explore these questions, we turn to demography, or the study of populations. Three of the most important components that affect the issues above are fertility, mortality, and migration.
At over 7 billion, Earth’s population is always on the move. (Photo courtesy of David Sim/flickr)
The fertility rate of a society is a measure noting the number of children born. The fertility number is generally lower than the fecundity number, which measures the potential number of children that could be born to women of childbearing age. Sociologists measure fertility using the crude birthrate (the number of live births per 1,000 people per year). Just as fertility measures childbearing, the mortality rate is a measure of the number of people who die. The crude death rate is a number derived from the number of deaths per 1,000 people per year. When analyzed together, fertility and mortality rates help researchers understand the overall growth occurring in a population.
Another key element in studying populations is the movement of people into and out of an area. Migration may take the form of immigration, which describes movement into an area to take up permanent residence, or emigration, which refers to movement out of an area to another place of permanent residence. Migration might be voluntary (as when college students study abroad), involuntary (as when Syrians evacuated war-torn areas), or forced (as when many Native American tribes were removed from the lands they’d lived in for generations).
Changing fertility, mortality, and migration rates make up the total population composition, a snapshot of the demographic profile of a population. This number can be measured for societies, nations, world regions, or other groups. The population composition includes the sex ratio, the number of men for every hundred women, as well as the population pyramid, a picture of population distribution by sex and age (Figure).
|Country||Population (in millions)||Fertility Rate||Mortality Rate||Sex Ratio Male to Female|
|United States of America||318.92||2.0%||8.2%||0.97|
Comparing the three countries in Table reveals that there are more men than women in Afghanistan, whereas the reverse is true in Sweden and the United States. Afghanistan also has significantly higher fertility and mortality rates than either of the other two countries. Do these statistics surprise you? How do you think the population makeup affects the political climate and economics of the different countries?
Sociologists have long looked at population issues as central to understanding human interactions. Below we will look at four theories about population that inform sociological thought: Malthusian, zero population growth, cornucopian, and demographic transition theories.
Thomas Malthus (1766–1834) was an English clergyman who made dire predictions about earth’s ability to sustain its growing population. According to Malthusian theory, three factors would control human population that exceeded the earth’s carrying capacity, or how many people can live in a given area considering the amount of available resources. Malthus identified these factors as war, famine, and disease (Malthus 1798). He termed them “positive checks” because they increase mortality rates, thus keeping the population in check. They are countered by “preventive checks,” which also control the population but by reducing fertility rates; preventive checks include birth control and celibacy. Thinking practically, Malthus saw that people could produce only so much food in a given year, yet the population was increasing at an exponential rate. Eventually, he thought people would run out of food and begin to starve. They would go to war over increasingly scarce resources and reduce the population to a manageable level, and then the cycle would begin anew.
Of course, this has not exactly happened. The human population has continued to grow long past Malthus’s predictions. So what happened? Why didn’t we die off? There are three reasons sociologists believe we are continuing to expand the population of our planet. First, technological increases in food production have increased both the amount and quality of calories we can produce per person. Second, human ingenuity has developed new medicine to curtail death from disease. Finally, the development and widespread use of contraception and other forms of family planning have decreased the speed at which our population increases. But what about the future? Some still believe Malthus was correct and that ample resources to support the earth’s population will soon run out.
Zero Population Growth
A neo-Malthusian researcher named Paul Ehrlich brought Malthus’s predictions into the twentieth century. However, according to Ehrlich, it is the environment, not specifically the food supply, that will play a crucial role in the continued health of planet’s population (Ehrlich 1968). Ehrlich's ideas suggest that the human population is moving rapidly toward complete environmental collapse, as privileged people use up or pollute a number of environmental resources such as water and air. He advocated for a goal of zero population growth (ZPG), in which the number of people entering a population through birth or immigration is equal to the number of people leaving it via death or emigration. While support for this concept is mixed, it is still considered a possible solution to global overpopulation.
Of course, some theories are less focused on the pessimistic hypothesis that the world’s population will meet a detrimental challenge to sustaining itself. Cornucopian theory scoffs at the idea of humans wiping themselves out; it asserts that human ingenuity can resolve any environmental or social issues that develop. As an example, it points to the issue of food supply. If we need more food, the theory contends, agricultural scientists will figure out how to grow it, as they have already been doing for centuries. After all, in this perspective, human ingenuity has been up to the task for thousands of years and there is no reason for that pattern not to continue (Simon 1981).
Demographic Transition Theory
Whether you believe that we are headed for environmental disaster and the end of human existence as we know it, or you think people will always adapt to changing circumstances, we can see clear patterns in population growth. Societies develop along a predictable continuum as they evolve from unindustrialized to postindustrial. Demographic transition theory (Caldwell and Caldwell 2006) suggests that future population growth will develop along a predictable four-stage model.
In Stage 1, birth, death, and infant mortality rates are all high, while life expectancy is short. An example of this stage is the 1800s in the United States. As countries begin to industrialize, they enter Stage 2, where birthrates are higher while infant mortality and the death rates drop. Life expectancy also increases. Afghanistan is currently in this stage. Stage 3 occurs once a society is thoroughly industrialized; birthrates decline, while life expectancy continues to increase. Death rates continue to decrease. Mexico’s population is at this stage. In the final phase, Stage 4, we see the postindustrial era of a society. Birth and death rates are low, people are healthier and live longer, and society enters a phase of population stability. Overall population may even decline. For example, Sweden is considered to be in Stage 4.
The United Nations Population Fund (2008) categorizes nations as high fertility, intermediate fertility, or low fertility. The United Nations (UN) anticipates the population growth will triple between 2011 and 2100 in high-fertility countries, which are currently concentrated in sub-Saharan Africa. For countries with intermediate fertility rates (the United States, India, and Mexico all fall into this category), growth is expected to be about 26 percent. And low-fertility countries like China, Australia, and most of Europe will actually see population declines of approximately 20 percent. The graphs below illustrate this trend.
Changes in U.S. Immigration Patterns and Attitudes
Projected Population in Africa. This graph shows the population growth of countries located on the African continent, many of which have high fertility rates. (Graph courtesy of USAID)
Projected Population in the United States. The United States has an intermediate fertility rate, and therefore, a comparatively moderate projected population growth. (Graph courtesy of USAID)
Projected Population in Europe. This chart shows the projected population growth of Europe for the remainder of this century. (Graph courtesy of USAID)
Worldwide patterns of migration have changed, though the United States remains the most popular destination. From 1990 to 2013, the number of migrants living in the United States increased from one in six to one in five (The Pew Research Center 2013). Overall, in 2013 the United States was home to about 46 million foreign-born people, while only about 3 million U.S. citizens lived abroad. Of foreign-born citizens emigrating to the United States, 55 percent originated in Latin America and the Caribbean (Connor, Cohn, and Gonzalez-Barrera 2013).
While there are more foreign-born people residing in the United States legally, as of 2012 about 11.7 million resided here without legal status (Passel, Cohn, and Gonzalez-Barrera 2013). Most citizens agree that our national immigration policies are in need major adjustment. Almost three-quarters of those in a recent national survey believed illegal immigrants should have a path to citizenship provided they meet other requirements, such as speaking English or paying restitution for the time they spent in the country illegally. Interestingly, 55 percent of those surveyed who identified as Hispanic think a pathway to citizenship is of secondary importance to provisions for living legally in the United States without the threat of deportation (The Pew Research Center 2013).
Scholars understand demography through various analyses. Malthusian, zero population growth, cornucopian theory, and demographic transition theories all help sociologists study demography. The earth’s human population is growing quickly, especially in peripheral countries. Factors that impact population include birthrates, mortality rates, and migration, including immigration and emigration. There are numerous potential outcomes of the growing population, and sociological perspectives vary on the potential effect of these increased numbers. The growth will pressure the already taxed planet and its natural resources.
Caldwell, John Charles and Bruce Caldwell. 2006. Demographic Transition Theory. The Netherlands: Springer.
CIA World Factbook. 2014. "Guide to Country Comparisons." Central Intelligence Agency World Factbook. Retrieved October 31, 2014 (https://www.cia.gov/library/publicat...rderguide.html).
Colborn, Theo, Carol Kwiatkowski, Kim Schultz, and Mary Bachran. 2011. "Natural Gas Operations from a Public Health Perspective." Human & Ecological Risk Assessment. 17 (5): 1039-1056
Connor, Phillip, D'Vera Cohn, and Ana Gonzalez-Barrera. 2013. "Changing Patterns of Global Migration and Remittances." Pew Research Centers Social Demographic Trends Project RSS. N.p., Retreived October 31, 2014 (http://www.pewsocialtrends.org/2013/...d-remittances/).
Dart, Tom. 2014. "Child Migrants at Texas Border: An Immigration Crisis That's Hardly New." The Guardian [Houston]. www.theguardian.com. Guardian News and Media Limited. Retrieved October 30, 2014 (http://www.theguardian.com/world/201...children-texas).
Ehrlich, Paul R. 1968. The Population Bomb. New York: Ballantine.
Environmental Protection Agency. 2014. "EPA's Study of Hydraulic Fracturing and Its Potential Impact on Drinking Water Resources." U.S. EPA, September 14. Retrieved October 29, 2014. (http://www2.epa.gov/hfstudy).
Fox News, and Associated Press. 2014. "Protests Turn Back Buses Carrying Illegal Immigrant Children." Fox News. FOX News Network. Retrieved October 30, 2014 (http://www.foxnews.com/us/2014/07/02...o-be-rerouted/).
Henry, Terrence. 2012. "How Fracking Disposal Wells Are Causing Earthquakes in Dallas-Fort Worth." Texas RSS. N.p., August 6. Retreived October 29, 2014 (http://stateimpact.npr.org/texas/2012/08/06/how-fracking-disposal-wells-are-causing-earthquakes-in-dallas-fort-worth/).
IHS Global Insights. 2012. "The Economic and Employment Contributions of Unconventional Gas Development in State Economies." Prepared for America's Natural Gas Alliance, June 2012. Retrieved October 29, 2014. (http://www.anga.us/media/content/F7D4500D-DD3A-1073-DA3480BE3CA41595/files/state_unconv_gas_economic_contribution.pdf).
Malthus, Thomas R. 1965 . An Essay on Population. New York: Augustus Kelley.
Passel, Jeffrey, D'Vera Cohn, and Ana Gonzalez-Barrera. 2013. "Population Decline of Unauthorized Immigrants Stalls, May Have Reversed." Pew Research Centers Hispanic Trends Project RSS. N.p., Retreieved October 31, 2014 (http://www.pewhispanic.org/2013/09/2...have-reversed/).
Pew Research Center. 2013. "Immigration: Key Data Points from Pew Research." Pew Research Center RSS. N.p., Retrieved October 31, 2014 (http://www.pewresearch.org/key-data-...ublic-opinion/).
Popescu, Roxana. 2014. "Frequently Asked Questions about the Migrant Crisis." U-T San Diego. San Diego Union-Tribue, Retreieved October 31, 2014 (http://www.utsandiego.com/news/2014/...nt-crisis-FAQ/).
Reyes, Raul A. 2014. "Murrieta Immigration Protests Were Unfortunate, Unnecessary." The Huffington Post. TheHuffingtonPost.com, Retrieved October 31, 2014 (http://www.huffingtonpost.com/raul-a...b_5569351.html).
Simon, Julian Lincoln. 1981. The Ultimate Resource. Princeton, NJ: Princeton University Press.
The United Nations Refugee Agency. 2014. "World Refugee Day: Global Forced Displacement Tops 50 Million for First Time in Post-World War II Era." UNHCR News. N.p., Retrieved October 31, 2014(http://www.unhcr.org/53a155bc6.html).
U.S. Congress. 2008. The William Wilberforce Trafficking Victims Protection Reauthorization Act of 2008. 7311, 110 Cong., U.S. G.P.O. (enacted). Print.
- carrying capacity
- the amount of people that can live in a given area considering the amount of available resources
- cornucopian theory
- a theory that asserts human ingenuity will rise to the challenge of providing adequate resources for a growing population
- demographic transition theory
- a theory that describes four stages of population growth, following patterns that connect birth and death rates with stages of industrial development
- the study of population
- fertility rate
- a measure noting the actual number of children born
- Malthusian theory
- a theory asserting that population is controlled through positive checks (war, famine, disease) and preventive checks (measures to reduce fertility)
- mortality rate
- a measure of the number of people in a population who die
- population composition
- a snapshot of the demographic profile of a population based on fertility, mortality, and migration rates
- population pyramid
- a graphic representation that depicts population distribution according to age and sex
- sex ratio
- the ratio of men to women in a given population
- zero population growth
- a theoretical goal in which the number of people entering a population through birth or immigration is equal to the number of people leaving it via death or emigration