Demography is a complicated field of study, and demographic discussions can often come across as pure jargon. As a result, the comforting response is often to accept the simplest, most fundamental arguments, such as those of Malthus and Ehrlich, to be true. In order to fully understand the intricate world of demography, one must be familiar with key terms and concepts, foundational knowledge that enables thinkers to formulate their own opinions instead of submitting to popular thought that is not always true. This page includes brief definitions and explanations of some key terms and concepts that have appeared on this website so that the reader can effectively interpret data, understand contemporary circumstances and arm themselves with the literacy necessary to conduct constructive dialogues about demography.
Demography:
“Demography [is the] statistical study of human populations, especially with reference to size and density, distribution, and vital statistics (births, marriages, deaths, etc.)” (Demography). This field of study is at the core of spatial discussion about human population, discussions such as the one in this website.
“Demography [is the] statistical study of human populations, especially with reference to size and density, distribution, and vital statistics (births, marriages, deaths, etc.)” (Demography). This field of study is at the core of spatial discussion about human population, discussions such as the one in this website.
Census:
“Census [is] an enumeration of people, houses, firms, or other important items in a country or region at a particular time” (Census). The census is conducted by the United States Census Bureau and is the main source of our demographic data. Other organizations that collect great data are the Pew Research Center and the World Bank. |
Population Explosion:
In just the past few centuries, human growth has accelerated at unprecedented rates, with the doubling time (the time it takes for a growing sample to double, in this case population) shrinking from generation to generation. To put this in perspective, the doubling time for the global human population to grow from 250 million to 500 million was over 16 centuries (the population reached 500 million around 1650 CE). The next doubling time that brought the human population to 1 billion in 1820, by comparison, was only 170 years. The next doubling took just over a century and the most recent complete doubling to 4 billion humans, took only 45 years, bringing us to 1975. There has never been this rapid a growth in the history of humanity, and this population explosion is what influenced thinkers such as Thomas Malthus and Paul Ehrlich.
For discussed reasons, however, doubling time is beginning to rise, and, as of now, doubling time to reach 8 billion people is estimated at around 54 years since 1975, bringing us to the late 2020s. With current demographic trends, this is projected to be the last doubling, and global human population is predicted to level off around 10 billion sometime in the 2050s. (de Blij et al, 51-53).
In just the past few centuries, human growth has accelerated at unprecedented rates, with the doubling time (the time it takes for a growing sample to double, in this case population) shrinking from generation to generation. To put this in perspective, the doubling time for the global human population to grow from 250 million to 500 million was over 16 centuries (the population reached 500 million around 1650 CE). The next doubling time that brought the human population to 1 billion in 1820, by comparison, was only 170 years. The next doubling took just over a century and the most recent complete doubling to 4 billion humans, took only 45 years, bringing us to 1975. There has never been this rapid a growth in the history of humanity, and this population explosion is what influenced thinkers such as Thomas Malthus and Paul Ehrlich.
For discussed reasons, however, doubling time is beginning to rise, and, as of now, doubling time to reach 8 billion people is estimated at around 54 years since 1975, bringing us to the late 2020s. With current demographic trends, this is projected to be the last doubling, and global human population is predicted to level off around 10 billion sometime in the 2050s. (de Blij et al, 51-53).
Malthusianism, Neo-Malthusianism and the Irish Potato Famine
Thomas Malthus (1766-1834) was an English economist and demographer. His Essay on the Principles of Population warned that humanity is facing the threats of overpopulation because human population will exceed food production capacity, leading to mass famine and death. His “cycle of misery” is founded on the facts that humanity grows exponentially, compounding on itself from generation to generation, while food production capacity grows linearly, only increasing according to the addition of new farmland that yields just as much as the rest without a multiplier effect. At the time of Malthus’ writing, this was very much true, but later became obsolete with the events of the Green Revolution, a relatively new agricultural revolution involving the use of chemical supplements (fertilizers, pesticides, etc.), genetic modification and mechanized factory farming to greatly increase yield per unit of agricultural land.
For the time being, the Green Revolution has created enough surplus to prevent the misery of the Malthusian cycle indefinitely. Neo-Malthusian thinkers, however, argue that the practices of the Green Revolution are highly unsustainable, and the longer we allow population to grow unchecked, the more miserable the cycle will prove.
Malthus believed that famine, plague, war and death all mitigate the cycle of misery. When the Irish Potato Famine began in the 1840s, British diplomatic officials with a Malthusian mindset took advantage of the opportunity to thin the human population by forcing the Irish to export what little produce they had to England and barring international aid from assisting the Irish in this humanitarian catastrophe. There are many facets to the complicated situation of the Irish Potato Famine, and this is one possible take on the demographic thinking behind the British course of action that decimated the Irish population.
Thomas Malthus (1766-1834) was an English economist and demographer. His Essay on the Principles of Population warned that humanity is facing the threats of overpopulation because human population will exceed food production capacity, leading to mass famine and death. His “cycle of misery” is founded on the facts that humanity grows exponentially, compounding on itself from generation to generation, while food production capacity grows linearly, only increasing according to the addition of new farmland that yields just as much as the rest without a multiplier effect. At the time of Malthus’ writing, this was very much true, but later became obsolete with the events of the Green Revolution, a relatively new agricultural revolution involving the use of chemical supplements (fertilizers, pesticides, etc.), genetic modification and mechanized factory farming to greatly increase yield per unit of agricultural land.
For the time being, the Green Revolution has created enough surplus to prevent the misery of the Malthusian cycle indefinitely. Neo-Malthusian thinkers, however, argue that the practices of the Green Revolution are highly unsustainable, and the longer we allow population to grow unchecked, the more miserable the cycle will prove.
Malthus believed that famine, plague, war and death all mitigate the cycle of misery. When the Irish Potato Famine began in the 1840s, British diplomatic officials with a Malthusian mindset took advantage of the opportunity to thin the human population by forcing the Irish to export what little produce they had to England and barring international aid from assisting the Irish in this humanitarian catastrophe. There are many facets to the complicated situation of the Irish Potato Famine, and this is one possible take on the demographic thinking behind the British course of action that decimated the Irish population.
Birth Rate, Death Rate, Natural Increase and Fertility Rates:
Crude birth rate (CBR) is the number of live births per thousand people in a population per year. Crude death rate (CDR) is the number of deaths per year per thousand people in a population. Natural increase is the difference between CBR and CDR for a certain year (de Blij et al, 55). These three statistics can be calculated on an annual basis and can mathematically explain population growth or decline in a certain year. Total fertility rate (TFR) is the focus of Last’s argument, and is an estimate of the average number of children born to a woman in her childbearing years (de Blij et al, 49). TFRs are calculated over extended periods of time and offer a window into what is occurring demographically during a certain period of time. A TFR of 2.1 is known as replacement level, and will stabilize population size. These key terms almost always arise in demographic discussions.
Crude birth rate (CBR) is the number of live births per thousand people in a population per year. Crude death rate (CDR) is the number of deaths per year per thousand people in a population. Natural increase is the difference between CBR and CDR for a certain year (de Blij et al, 55). These three statistics can be calculated on an annual basis and can mathematically explain population growth or decline in a certain year. Total fertility rate (TFR) is the focus of Last’s argument, and is an estimate of the average number of children born to a woman in her childbearing years (de Blij et al, 49). TFRs are calculated over extended periods of time and offer a window into what is occurring demographically during a certain period of time. A TFR of 2.1 is known as replacement level, and will stabilize population size. These key terms almost always arise in demographic discussions.
Demographic Transition Model and Population Pyramids:
Population Bulge, Aging Population and the Baby Boom:
When reading a population pyramid, one may notice a particular bulge or contraction around a certain age group. Bulges are typically caused by abnormally high fertility or immigration over a certain period of time, while contractions either indicate abnormally low fertility caused by war, famine or plague, or high emigration. In Kenya’s population pyramid for 2000, high fertility and low overall life expectancy are possible explanations to the youth bulge shown. In the United States’ population pyramids, the Great Depression and the Baby Boom caused the indicated contraction and bulge.
When reading a population pyramid, one may notice a particular bulge or contraction around a certain age group. Bulges are typically caused by abnormally high fertility or immigration over a certain period of time, while contractions either indicate abnormally low fertility caused by war, famine or plague, or high emigration. In Kenya’s population pyramid for 2000, high fertility and low overall life expectancy are possible explanations to the youth bulge shown. In the United States’ population pyramids, the Great Depression and the Baby Boom caused the indicated contraction and bulge.
In simplest terms, the Baby Boom was sparked when American veterans returned home from Europe, North Africa and the Pacific following the resolution of WWII. General confidence in American prosperity combined with the suburban revolution caused fertility to skyrocket, creating the visible bulge in American population. As these Baby Boomers represent a heavy weight of American population, their aging characterizes America with an aging population.
Dependency Ratios:
“Age dependency ratio is the ratio of dependents--people younger than 15 or older than 64--to the working-age population--those ages 15-64. Data are shown as the proportion of dependents per 100 working-age population” (Age Dependency Ratio). A dependency ratio can inform us about a country’s demographic state because high dependency ratios typically indicate extremes of population change. A rapidly growing population has a youth bulge (population bulge of youth), thus placing many dependents on less workers. An aging population (nearing contraction) places many dependents on less workers while also increasing pressure on the workers to pay for social security. Low dependency ratios show a country with a stable population and a relatively strong working class.
“Age dependency ratio is the ratio of dependents--people younger than 15 or older than 64--to the working-age population--those ages 15-64. Data are shown as the proportion of dependents per 100 working-age population” (Age Dependency Ratio). A dependency ratio can inform us about a country’s demographic state because high dependency ratios typically indicate extremes of population change. A rapidly growing population has a youth bulge (population bulge of youth), thus placing many dependents on less workers. An aging population (nearing contraction) places many dependents on less workers while also increasing pressure on the workers to pay for social security. Low dependency ratios show a country with a stable population and a relatively strong working class.
Demographic Momentum and Migration:
Regardless of drops in fertility or natural increase, population will not contract until a generational bulge beings to die. This is known as demographic momentum. In the case of the United States, dangerously low fertility has not yet caused mass population contraction because death rates do not yet exceed birth rates. Within a few decades, however, the bulge of Baby Boomers will begin to die, and death rates will suddenly proportionally outnumber birth rates. This is the point where a population begins to contract. The same concept can be applied to a situation where a population continues to decline regardless of fertility increase.
Demographic momentum is aided by migration. A population can continue to grow or decline because of mass immigration or emigration. Once these migration trends come to an end, a population can suddenly react to its rate of natural increase through sudden expansion or contraction. It is important to understand the impacts of demographic momentum and migration because they serve as a guise for looming demographic transition. An continually increasing population conflicts with the warnings of demographers about population contractions, sometimes delaying action until it is too late. |
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China’s One Child Policy:
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China’s One Child Policy caused an aging population bulge through sudden contraction. Today, this bulge is aging and changing China’s dependency ratio by imposing an increasing number of elderly dependents on a decreasing number of workers. Due to demographic momentum, the repealing of this policy will not mitigate the weight China’s demographic structure until the new youth bulge reaches working age.
If any concepts or terms are missing on this page, please do not hesitate to contact me so that I can include them. My objective is to enable the reader to understand all relevant aspects of the foreign field of demography.
Ben Squarer
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AP Human Geography
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What to Expect When No One's Expecting by Jonathan V. Last
AP Human Geography
May 23, 2016