Knowt
Chapter 3 | Patterns of Population
3.1 Where People Live
Why Study Population?
According to the UN, the global population reached 7.8 billion in December 2019.
Two-thirds of that population can be found in four regions: East Asia, South Asia, Southeast Asia, and Western Europe.
During the second half of the 20th century, the world’s population increased at a faster rate than ever before. Today, more people are alive than at any other time in Earth’s history.
These facts lead geographers to analyze the complex reasons populations grow, spread, and the challenges that results in.
They analyze where people live, differences among populations, changes within populations, and the reasons for each.
Population Distribution: Where people live in a geographic area
Population distribution affects the cultural, political, environmental, and economic aspects and conditions in any given area.
Global distributions of people are influenced by physical, environmental, and human factors.
At every scale—from local to global—there are identifiable factors that influence population distribution.
These interconnected factors are liable to change, which means that populations will change with them.
Physical and Environmental Factors
Humans depend on the environment for their survival, so they are more likely to settle where there are moderate climates, rich soils, and adequate water supplies.
Most people tend to live in areas that are not too hot, too dry, too wet, or too cold.
Coasts and waterways are often densely populated because they offer economic advantages and convenient transportation routes.
Populations are most heavily concentrated at low elevations and diminish rapidly as the elevation increases.
Climate
Climate: The long-term patterns of weather in a particular area
Climate helps shape the soil, vegetation, and agricultural opportunities of an environment.
A region’s growing season is determined by the region’s climate and is important for the support of human life.
Temperate climate: A climate with moderate temperatures and adequate precipitation amounts
Temperate climates are generally more densely populated.
As technology continues to develop, humans engineer new ways to live in previously uninhabitable areas.
Some places with extreme climates are so hostile that even with new technology they cannot become easily habitable: The arid Sahara in North Africa or the subarctic and polar climates in much of Canada.
These areas tend to be less populated because of the extreme impact of the climate and the climate’s effect on agriculture.
Landforms
Landforms: The natural features of Earth’s surface
Landforms also affect population distribution.
Habitable land has adequate water sources, relatively flat terrain, and the potential to produce food.
Areas next to rivers typically have rich soils that agricultural communities rely on.
River valleys across the world have long supported dense populations.
Rocky, steep regions are typically less populated due to the difficulty of building structures and transportation links such as roads and railways.
Mountainous regions are remote and difficult to access and to live in; the air contains less oxygen than at sea level.
These same areas present challenges agriculturally because higher elevations result in much colder temperatures.
Water Accessibility
Ready access to fresh, ample water is essential for human survival and development and thus is a key factor in population distribution.
People use surface water supplies like rivers, lakes, and oases and also access underground water sources (aquifers.)
Water is needed not only for agriculture but also for industrial use, sanitation, and hygiene.
Areas that are dry or that suffer from regular drought are difficult for people to inhabit.
Technology and innovation have helped some people live in drier areas.
Human Factors
In addition to physical and environmental factors, changing human factors—such as economics, politics, culture, and history—influence the distribution of human populations.
Economic Factors
People tend to live where they can earn a living through agriculture, natural resource extraction, manufacturing, sales, and a variety of other activities.
The degree of opportunity for economic activity within an area influences population distribution.
An increase in technologically advanced and global economic activities has resulted in a significant redistribution of population.
Human migration: The permanent movement of people from one place to another
Though the reasons behind migration are complex and often numerous, people are often influenced to migrate for economic reasons
Areas that provide economic opportunity may become densely populated even though the environment presents conditions that are otherwise challenging for human habitation.
Political Factors
People who are dissatisfied with their government or political system may voluntarily migrate to another country or region within the same country.
Unstable political circumstances or war may also compel citizens to leave their home countries or regions.
Governments sometimes create policy to redistribute population and encourage migration.
Cultural Factors
Housing availability, safety, access to transportation, and a feeling of belonging and community are cultural factors that may serve as reasons to live in a certain place.
Once an area is settled, it tends to stay settled and increase its population as long as the initial reasons for habitation persist.
Cultural factors that influence changes in population include religion, the roles and status of women, and familial attitudes regarding marriage and children.
Historical Factors
History, the significant events that took place in the past, is often intertwined with other physical, environmental, and human factors.
The population distribution of the past can influence the population distribution of today and tomorrow.
The historical duration of settlements in a region and that region’s present population concentration are often linked.
Many of the densely populated areas of the world have an long history of human habitation, while sparse populations in certain areas tend to have a less established history of human habitation.
The human, physical, and environmental factors that influenced population distribution in an area may change which will cause a trend in population distribution to also change.
Measuring Population Density
By 1800, Earth’s population had reached 1 billion.
Asia does and has, historically, always had the more concentrated population.
60 percent of the world’s 7.8 billion people live in Asia.
Population density: The number of people occupying a unit of land
Geographers use three methods to calculate population density: arithmetic density, physiological density, and agricultural density.
Each method uses a different land unit to provide key information about the pressure population exerts on the land.
Arithmetic Density
Arithmetic Density: The total number of people per unit area of land; also called crude density
Though this method is used most frequently to calculate population density, arithmetic density is also called crude density because it does not account for land that is difficult to live on or uninhabitable.
It is the most general of the three density measures because it provides an average density with no information about distribution patterns like clustering or dispersion.
Physiological Density
Physiological density: The total number of people per unit of arable land
Arable land: Land that can be used to grow crops
Physiological density provides insight into whether people can sustain themselves agriculturally.
The higher the physiological density, the greater the pressure on the land and its resources.
Comparing arithmetic and physiological densities helps geographers understand the capacity of the land and its resources to support the needs of the population living on it.
Agricultural Density
Agricultural density: The total number of farmers per unit of arable land
Agricultural density can reveal more about a country’s wealth than its population distribution.
This measurement doesn’t supply data about how much technology and money can be put into cultivation.
Countries with similar physiological densities but different economic conditions tend to produce vastly different amounts of food or other crops.
Not all arable land is equal.
A higher agricultural density suggests that most of the farming taking place is providing crops and livestock for only the farmers’ families and close community.
Subsistence agriculture: An agricultural practice that provides crops or livestock for only the farmers’ families and close community
Subsistence agriculture is common in peripheral and semi-peripheral countries where there are fewer mechanical resources available to work the land and more people are needed to care for crops and livestock.
This method can include modifications such as irrigation that greatly impact the environment.
Everything is designed to get the greatest yield from small fields.
The different economic structures of countries may be reflected in their agricultural density measurements.
A country’s access to technology and other resources allows for fewer people to farm extensive land areas, while still feeding many people.
Technology that feeds more people may seem good, but it can have long-term harmful effects on the environment.
Agricultural density data help geographers understand how much food is being produced.
Comparing physiological density and agricultural density helps geographers analyze the overall impact on the environment.
3.2 Consequences of Population Density
Impact of Population Distribution on Society
Distribution and density of Earth’s population reflect its landforms, soils, vegetation, climate types, available resources, and levels of economic development.
People are the driving forces behind factors that impact the environment, such as pollution, resource depletion, and land degradation.
Geographers want to know where people live and the consequences of population distribution (crowding, isolation, unequal access to services/resources, environmental impacts) which ultimately affect the quality of human life and human society.
The more people who are born into or move to an area, the greater the need for access to adequate housing, jobs, and fresh water, and services like sanitation and health care.
Providing services to clustered populations is easier than providing them to dispersed populations.
People who live further from services are less likely to be able to utilize them.
Social services are more effective when the population they serve is clustered because costs are lower when the services can reach more people in less distance.
Rough terrain can also impair social services’ ability to access those in need.
Clustered distributions with high populations demand more of the services, however.
The higher the hazard level, the greater the risk, which requires more specialized resources to mitigate.
Increases in population densities can also lead to disparities in economic growth between the areas where populations are clustered versus the areas where populations are scattered.
There may be stark contrasts in wages, opportunities, and access to health care between the core and periphery.
Unlike scattered, sparsely populated areas, evenly and densely populated areas usually have more economic development and therefore more power.
Impact of Human Distribution on the Environment
As a population grows, greater pressure is placed on arable land, water, energy, and natural resources to provide an adequate supply of food.
It becomes harder to maintain a balance with the environment.
Greater population densities can strain resources, such as clean water, and the possibility of exhausting an environment’s resources can become reality.
Carrying capacity: The maximum population size an environment can sustain
A key concept originating from biology, carrying capacity represents the threshold at which the population of a species levels off at an environmentally determined maximum because of a shortage of resources.
Geographers use this term when discussing the limits that human populations face in various regions and at a range of scales.
The carrying capacity of Earth has yet to be determined.
An area with a high population density may not be considered overpopulated if the area has a high carrying capacity, which could be the result of fertile soil or modern farming methods.
Greater population densities can lead to environmental degradation if the carrying capacity is unable to sustain the population.
Urban areas with dense populations impact the environment more through pollution and resource use.
Cities consume more resources and create pollution from additional vehicles, heating and cooling sources, and industrialization/manufacturing.
High levels of consumption in densely populated areas also have environmental impacts through the use of large amounts of energy and the generation of excess amounts of waste.
Some city officials and researchers are developing ways to use resources more efficiently/lessen the environmental impact of urban areas.
By analyzing the population density and carrying capacity of an area, geographers can better understand how a changing population interacts with its environment.
Resources such as air quality, food supply, biodiversity, and safe water can be monitored to find ways to extend an environment’s carrying capacity or prevent a population from exceeding the environmental limit.
3.3 Population Composition
Dependency Ratio
The age structure of a population has significant government policy and economic implications.
Geographers analyze these and other age-related demographic studies using ratios for specific age groups.
Dependency ratio: The number of people in a dependent age group (under age 15 or age 65 and older) divided by the number of people in the working-age group (age 15 to 64), multiplied by 100
The dependency ratio is used as an indicator to measure the demand placed on the working-age population to provide for the dependent population.
In reality, the workforce includes people older than 64 and younger than 15.
It is also incorrect to assume that everyone ages 15 to 64 is working.
Dependency Ratios and Economic Development
The size of the dependent population relative to the size of the working-age population is a key factor influencing economic development.
Dependency ratios are useful when comparing societies over time and when comparing different areas.
They are also used at all levels to predict productivity at a large-scale level.
Monitoring these ratios provides insight into the policies that countries may need as their population ages and changes.
A higher dependency ratio indicates fewer people of working age and fewer people in the workforce earning income and paying taxes.
This means that in a country with a high dependency ratio, people of working age (and the overall economy) encounter greater pressure.
As the percentage of nonworking people rises, people who are working may face increased taxes to compensate for a larger dependent population.
Ideally, an economy should have a smaller dependency ratio, with a constant flow of people entering the workforce, and a smaller number exiting the working-age population each year.
Data Beneath a Dependency Ratio
In most of the world’s countries, fewer babies are being born, and the number of elderly people continues to rise.
The fastest-growing segment of the world population is people age 65 and older.
Dependency ratios are increasing, and countries with aging populations will struggle with how to support their elderly.
Although this scenario applies to most countries, others continue to see rapid population growth, with one of the largest segments being the youngest.
In this case, countries with growing younger segments could at some point have the same dependency ratio as countries with growing older segments.
For example: Japan and Namibia have similar dependency ratios, but just looking at the number can be misleading.
Japan has a high elderly dependency, and Namibia has a high youth dependency. Despite having the same statistics, it’s important to look behind the data to see the truth.
Examining dependencies at various scales is important as well.
Sex Ratio
Sex ratio: The proportion of males to females in a population
Slightly more males than females are born. Women tend to live five or more years longer than men do.
In peripheral countries, the number of women who die during childbirth contributes to a lower percentage of women.
Societies with a high rate of emigration where men rather than women are more likely to migrate elsewhere will have more females than males.
War can also create differences because typically more men than women die in war.
There can also be time periods or regions where sex-selective abortions are common, contributing to differences.
The sex ratio is an important social indicator as it affects marriage rates, women’s labor-market participation rates, and the socialization of men and women within their cultural norms.
It also impacts fertility rates, birth rates, and the natural rate at which a population grows.
3.4 Measuring Growth and Decline
Fertility
Demographics: Data about the structures and characteristics of human populations
Fertility: The ability to produce children
Experts analyze the growth or decline of populations at various scales because the data impacts the natural environment and society, in the form of human health and the economy.
Governments and public health officials study fertility rates to see if the population will grow, decline, or stay the same.
As the population rises, pressure increases on the agricultural and housing sectors to provide food and shelter.
Experts in public health use data to predict and plan for health care.
Fertility also affects budgets and policies surrounding education.
International organizations, such as the United Nations, measure fertility to help solve international problems and make decisions about where to focus global resources.
Measures of Fertility
Crude birth rate: The number of births in a given year per 1,000 people in a given population
The CBR can be misleading in certain areas, like if a country is experiencing an influx of immigrating men for labor jobs, the CBR may be skewed.
CBR is still useful for geographers to calculate the rate of natural increase and population growth or decline in a country or at another scale.
Total fertility rate: The average number of children one woman in a given region will have during her child-bearing years (ages 15 to 49)
This rate relates births to an age and gender-specific group.
It helps eliminate distortions that may arise because of different age and sex distributions among populations; therefore, the TFR provides a better comparison of fertility levels across countries and populations than CBR measurements.
The TFR is also viewed as a more meaningful statistic than CBR because it helps reveal where the population is growing or shrinking.
A country’s TFR can be impacted by government policy, war or conflict, increased urbanization, economic stability or instability, higher levels of education among women, higher rates of women participating in the labor force, and the influence of culture and society.
The TFR is often a direct expression of a country’s healthcare system because it reflects a population’s access to doctors, nurses, hospitals, and medicine.
Mortality
Mortality: Deaths as a component of population change
Circumstances that affect the mortality rate include the availability and affordability of health care as well as clean water, adequate food, and shelter.
Measures of Mortality
Crude death rate: The number of deaths in a given year per 1,000 people in a given population
Core countries tend to have a higher CDR than peripheral countries do, but generalizations of CDRs can be misleading.
A high CDR can result from a lack of access to sanitation leading to poor health, but it can also be caused by a country with a high population of elderly people who contribute to the death rate greatly.
Infant mortality rate: The number of deaths of children under the age of 1 per 1,000 live births
The IMR is often considered a better indicator than the CDR in terms of health and health care in a country.
Infant mortality is high when medicine and maternal care are limited, and lower when access to clean water, sanitation, and public health is inadequate.
Life expectancy: The average number of years a person is expected to live
In core countries, the average life expectancy is more than 80 years old; in peripheral countries, it’s around 50 years.
It is important to note that people in peripheral countries can still grow as old as old people in core countries.
The primary reason their life expectancy is so low is generally because there are so many infants dying at ‘0,’ weighing their average down greatly.
Bearing in mind that scale can be an issue, geographers study fertility and mortality rates across global, national, and local scales.
Regional averages can disguise significant variation among countries, and country-level measurements can mask dramatic local variations, such as urban versus rural, male versus female, and wealthy versus poor.
Ethnic and cultural variations that exist within some countries, such as the vast differences among states in the United States and India, must also be considered.
Visualizing Population Composition with Population Pyramids
Population pyramid: A graph that shows the age-sex distribution of a given population
Projections and trends revealed in population pyramids predict what goods and services are needed, such as schools, elder care, and health care, and what to plan for in the future.
Countries with rapid population growth have a large-based and narrow-topped population pyramid, indicating a high child dependency ratio.
This shape can also signify a peripheral country as it results from high birth rates that supply increasingly more people into the lowest bars of the pyramid and in turn shrink the relative number of people in the oldest stages.
As the death rate declines, more people survive to reproductive ages and beyond.
As these people reproduce, the pyramid base widens.
Peripheral and semi-peripheral countries that have experienced improvements in life expectancy but continue to have high birth rates tend to have this shape.
The pattern reflects a history of rapid population growth and the potential for future rapid growth.
The narrow top is the result of a smaller number of births for many years in the past (when the population was much smaller) and higher death rates at older ages.
Chapter 3 | Patterns of Population
3.1 Where People Live
Why Study Population?
According to the UN, the global population reached 7.8 billion in December 2019.
Two-thirds of that population can be found in four regions: East Asia, South Asia, Southeast Asia, and Western Europe.
During the second half of the 20th century, the world’s population increased at a faster rate than ever before. Today, more people are alive than at any other time in Earth’s history.
These facts lead geographers to analyze the complex reasons populations grow, spread, and the challenges that results in.
They analyze where people live, differences among populations, changes within populations, and the reasons for each.
Population Distribution: Where people live in a geographic area
Population distribution affects the cultural, political, environmental, and economic aspects and conditions in any given area.
Global distributions of people are influenced by physical, environmental, and human factors.
At every scale—from local to global—there are identifiable factors that influence population distribution.
These interconnected factors are liable to change, which means that populations will change with them.
Physical and Environmental Factors
Humans depend on the environment for their survival, so they are more likely to settle where there are moderate climates, rich soils, and adequate water supplies.
Most people tend to live in areas that are not too hot, too dry, too wet, or too cold.
Coasts and waterways are often densely populated because they offer economic advantages and convenient transportation routes.
Populations are most heavily concentrated at low elevations and diminish rapidly as the elevation increases.
Climate
Climate: The long-term patterns of weather in a particular area
Climate helps shape the soil, vegetation, and agricultural opportunities of an environment.
A region’s growing season is determined by the region’s climate and is important for the support of human life.
Temperate climate: A climate with moderate temperatures and adequate precipitation amounts
Temperate climates are generally more densely populated.
As technology continues to develop, humans engineer new ways to live in previously uninhabitable areas.
Some places with extreme climates are so hostile that even with new technology they cannot become easily habitable: The arid Sahara in North Africa or the subarctic and polar climates in much of Canada.
These areas tend to be less populated because of the extreme impact of the climate and the climate’s effect on agriculture.
Landforms
Landforms: The natural features of Earth’s surface
Landforms also affect population distribution.
Habitable land has adequate water sources, relatively flat terrain, and the potential to produce food.
Areas next to rivers typically have rich soils that agricultural communities rely on.
River valleys across the world have long supported dense populations.
Rocky, steep regions are typically less populated due to the difficulty of building structures and transportation links such as roads and railways.
Mountainous regions are remote and difficult to access and to live in; the air contains less oxygen than at sea level.
These same areas present challenges agriculturally because higher elevations result in much colder temperatures.
Water Accessibility
Ready access to fresh, ample water is essential for human survival and development and thus is a key factor in population distribution.
People use surface water supplies like rivers, lakes, and oases and also access underground water sources (aquifers.)
Water is needed not only for agriculture but also for industrial use, sanitation, and hygiene.
Areas that are dry or that suffer from regular drought are difficult for people to inhabit.
Technology and innovation have helped some people live in drier areas.
Human Factors
In addition to physical and environmental factors, changing human factors—such as economics, politics, culture, and history—influence the distribution of human populations.
Economic Factors
People tend to live where they can earn a living through agriculture, natural resource extraction, manufacturing, sales, and a variety of other activities.
The degree of opportunity for economic activity within an area influences population distribution.
An increase in technologically advanced and global economic activities has resulted in a significant redistribution of population.
Human migration: The permanent movement of people from one place to another
Though the reasons behind migration are complex and often numerous, people are often influenced to migrate for economic reasons
Areas that provide economic opportunity may become densely populated even though the environment presents conditions that are otherwise challenging for human habitation.
Political Factors
People who are dissatisfied with their government or political system may voluntarily migrate to another country or region within the same country.
Unstable political circumstances or war may also compel citizens to leave their home countries or regions.
Governments sometimes create policy to redistribute population and encourage migration.
Cultural Factors
Housing availability, safety, access to transportation, and a feeling of belonging and community are cultural factors that may serve as reasons to live in a certain place.
Once an area is settled, it tends to stay settled and increase its population as long as the initial reasons for habitation persist.
Cultural factors that influence changes in population include religion, the roles and status of women, and familial attitudes regarding marriage and children.
Historical Factors
History, the significant events that took place in the past, is often intertwined with other physical, environmental, and human factors.
The population distribution of the past can influence the population distribution of today and tomorrow.
The historical duration of settlements in a region and that region’s present population concentration are often linked.
Many of the densely populated areas of the world have an long history of human habitation, while sparse populations in certain areas tend to have a less established history of human habitation.
The human, physical, and environmental factors that influenced population distribution in an area may change which will cause a trend in population distribution to also change.
Measuring Population Density
By 1800, Earth’s population had reached 1 billion.
Asia does and has, historically, always had the more concentrated population.
60 percent of the world’s 7.8 billion people live in Asia.
Population density: The number of people occupying a unit of land
Geographers use three methods to calculate population density: arithmetic density, physiological density, and agricultural density.
Each method uses a different land unit to provide key information about the pressure population exerts on the land.
Arithmetic Density
Arithmetic Density: The total number of people per unit area of land; also called crude density
Though this method is used most frequently to calculate population density, arithmetic density is also called crude density because it does not account for land that is difficult to live on or uninhabitable.
It is the most general of the three density measures because it provides an average density with no information about distribution patterns like clustering or dispersion.
Physiological Density
Physiological density: The total number of people per unit of arable land
Arable land: Land that can be used to grow crops
Physiological density provides insight into whether people can sustain themselves agriculturally.
The higher the physiological density, the greater the pressure on the land and its resources.
Comparing arithmetic and physiological densities helps geographers understand the capacity of the land and its resources to support the needs of the population living on it.
Agricultural Density
Agricultural density: The total number of farmers per unit of arable land
Agricultural density can reveal more about a country’s wealth than its population distribution.
This measurement doesn’t supply data about how much technology and money can be put into cultivation.
Countries with similar physiological densities but different economic conditions tend to produce vastly different amounts of food or other crops.
Not all arable land is equal.
A higher agricultural density suggests that most of the farming taking place is providing crops and livestock for only the farmers’ families and close community.
Subsistence agriculture: An agricultural practice that provides crops or livestock for only the farmers’ families and close community
Subsistence agriculture is common in peripheral and semi-peripheral countries where there are fewer mechanical resources available to work the land and more people are needed to care for crops and livestock.
This method can include modifications such as irrigation that greatly impact the environment.
Everything is designed to get the greatest yield from small fields.
The different economic structures of countries may be reflected in their agricultural density measurements.
A country’s access to technology and other resources allows for fewer people to farm extensive land areas, while still feeding many people.
Technology that feeds more people may seem good, but it can have long-term harmful effects on the environment.
Agricultural density data help geographers understand how much food is being produced.
Comparing physiological density and agricultural density helps geographers analyze the overall impact on the environment.
3.2 Consequences of Population Density
Impact of Population Distribution on Society
Distribution and density of Earth’s population reflect its landforms, soils, vegetation, climate types, available resources, and levels of economic development.
People are the driving forces behind factors that impact the environment, such as pollution, resource depletion, and land degradation.
Geographers want to know where people live and the consequences of population distribution (crowding, isolation, unequal access to services/resources, environmental impacts) which ultimately affect the quality of human life and human society.
The more people who are born into or move to an area, the greater the need for access to adequate housing, jobs, and fresh water, and services like sanitation and health care.
Providing services to clustered populations is easier than providing them to dispersed populations.
People who live further from services are less likely to be able to utilize them.
Social services are more effective when the population they serve is clustered because costs are lower when the services can reach more people in less distance.
Rough terrain can also impair social services’ ability to access those in need.
Clustered distributions with high populations demand more of the services, however.
The higher the hazard level, the greater the risk, which requires more specialized resources to mitigate.
Increases in population densities can also lead to disparities in economic growth between the areas where populations are clustered versus the areas where populations are scattered.
There may be stark contrasts in wages, opportunities, and access to health care between the core and periphery.
Unlike scattered, sparsely populated areas, evenly and densely populated areas usually have more economic development and therefore more power.
Impact of Human Distribution on the Environment
As a population grows, greater pressure is placed on arable land, water, energy, and natural resources to provide an adequate supply of food.
It becomes harder to maintain a balance with the environment.
Greater population densities can strain resources, such as clean water, and the possibility of exhausting an environment’s resources can become reality.
Carrying capacity: The maximum population size an environment can sustain
A key concept originating from biology, carrying capacity represents the threshold at which the population of a species levels off at an environmentally determined maximum because of a shortage of resources.
Geographers use this term when discussing the limits that human populations face in various regions and at a range of scales.
The carrying capacity of Earth has yet to be determined.
An area with a high population density may not be considered overpopulated if the area has a high carrying capacity, which could be the result of fertile soil or modern farming methods.
Greater population densities can lead to environmental degradation if the carrying capacity is unable to sustain the population.
Urban areas with dense populations impact the environment more through pollution and resource use.
Cities consume more resources and create pollution from additional vehicles, heating and cooling sources, and industrialization/manufacturing.
High levels of consumption in densely populated areas also have environmental impacts through the use of large amounts of energy and the generation of excess amounts of waste.
Some city officials and researchers are developing ways to use resources more efficiently/lessen the environmental impact of urban areas.
By analyzing the population density and carrying capacity of an area, geographers can better understand how a changing population interacts with its environment.
Resources such as air quality, food supply, biodiversity, and safe water can be monitored to find ways to extend an environment’s carrying capacity or prevent a population from exceeding the environmental limit.
3.3 Population Composition
Dependency Ratio
The age structure of a population has significant government policy and economic implications.
Geographers analyze these and other age-related demographic studies using ratios for specific age groups.
Dependency ratio: The number of people in a dependent age group (under age 15 or age 65 and older) divided by the number of people in the working-age group (age 15 to 64), multiplied by 100
The dependency ratio is used as an indicator to measure the demand placed on the working-age population to provide for the dependent population.
In reality, the workforce includes people older than 64 and younger than 15.
It is also incorrect to assume that everyone ages 15 to 64 is working.
Dependency Ratios and Economic Development
The size of the dependent population relative to the size of the working-age population is a key factor influencing economic development.
Dependency ratios are useful when comparing societies over time and when comparing different areas.
They are also used at all levels to predict productivity at a large-scale level.
Monitoring these ratios provides insight into the policies that countries may need as their population ages and changes.
A higher dependency ratio indicates fewer people of working age and fewer people in the workforce earning income and paying taxes.
This means that in a country with a high dependency ratio, people of working age (and the overall economy) encounter greater pressure.
As the percentage of nonworking people rises, people who are working may face increased taxes to compensate for a larger dependent population.
Ideally, an economy should have a smaller dependency ratio, with a constant flow of people entering the workforce, and a smaller number exiting the working-age population each year.
Data Beneath a Dependency Ratio
In most of the world’s countries, fewer babies are being born, and the number of elderly people continues to rise.
The fastest-growing segment of the world population is people age 65 and older.
Dependency ratios are increasing, and countries with aging populations will struggle with how to support their elderly.
Although this scenario applies to most countries, others continue to see rapid population growth, with one of the largest segments being the youngest.
In this case, countries with growing younger segments could at some point have the same dependency ratio as countries with growing older segments.
For example: Japan and Namibia have similar dependency ratios, but just looking at the number can be misleading.
Japan has a high elderly dependency, and Namibia has a high youth dependency. Despite having the same statistics, it’s important to look behind the data to see the truth.
Examining dependencies at various scales is important as well.
Sex Ratio
Sex ratio: The proportion of males to females in a population
Slightly more males than females are born. Women tend to live five or more years longer than men do.
In peripheral countries, the number of women who die during childbirth contributes to a lower percentage of women.
Societies with a high rate of emigration where men rather than women are more likely to migrate elsewhere will have more females than males.
War can also create differences because typically more men than women die in war.
There can also be time periods or regions where sex-selective abortions are common, contributing to differences.
The sex ratio is an important social indicator as it affects marriage rates, women’s labor-market participation rates, and the socialization of men and women within their cultural norms.
It also impacts fertility rates, birth rates, and the natural rate at which a population grows.
3.4 Measuring Growth and Decline
Fertility
Demographics: Data about the structures and characteristics of human populations
Fertility: The ability to produce children
Experts analyze the growth or decline of populations at various scales because the data impacts the natural environment and society, in the form of human health and the economy.
Governments and public health officials study fertility rates to see if the population will grow, decline, or stay the same.
As the population rises, pressure increases on the agricultural and housing sectors to provide food and shelter.
Experts in public health use data to predict and plan for health care.
Fertility also affects budgets and policies surrounding education.
International organizations, such as the United Nations, measure fertility to help solve international problems and make decisions about where to focus global resources.
Measures of Fertility
Crude birth rate: The number of births in a given year per 1,000 people in a given population
The CBR can be misleading in certain areas, like if a country is experiencing an influx of immigrating men for labor jobs, the CBR may be skewed.
CBR is still useful for geographers to calculate the rate of natural increase and population growth or decline in a country or at another scale.
Total fertility rate: The average number of children one woman in a given region will have during her child-bearing years (ages 15 to 49)
This rate relates births to an age and gender-specific group.
It helps eliminate distortions that may arise because of different age and sex distributions among populations; therefore, the TFR provides a better comparison of fertility levels across countries and populations than CBR measurements.
The TFR is also viewed as a more meaningful statistic than CBR because it helps reveal where the population is growing or shrinking.
A country’s TFR can be impacted by government policy, war or conflict, increased urbanization, economic stability or instability, higher levels of education among women, higher rates of women participating in the labor force, and the influence of culture and society.
The TFR is often a direct expression of a country’s healthcare system because it reflects a population’s access to doctors, nurses, hospitals, and medicine.
Mortality
Mortality: Deaths as a component of population change
Circumstances that affect the mortality rate include the availability and affordability of health care as well as clean water, adequate food, and shelter.
Measures of Mortality
Crude death rate: The number of deaths in a given year per 1,000 people in a given population
Core countries tend to have a higher CDR than peripheral countries do, but generalizations of CDRs can be misleading.
A high CDR can result from a lack of access to sanitation leading to poor health, but it can also be caused by a country with a high population of elderly people who contribute to the death rate greatly.
Infant mortality rate: The number of deaths of children under the age of 1 per 1,000 live births
The IMR is often considered a better indicator than the CDR in terms of health and health care in a country.
Infant mortality is high when medicine and maternal care are limited, and lower when access to clean water, sanitation, and public health is inadequate.
Life expectancy: The average number of years a person is expected to live
In core countries, the average life expectancy is more than 80 years old; in peripheral countries, it’s around 50 years.
It is important to note that people in peripheral countries can still grow as old as old people in core countries.
The primary reason their life expectancy is so low is generally because there are so many infants dying at ‘0,’ weighing their average down greatly.
Bearing in mind that scale can be an issue, geographers study fertility and mortality rates across global, national, and local scales.
Regional averages can disguise significant variation among countries, and country-level measurements can mask dramatic local variations, such as urban versus rural, male versus female, and wealthy versus poor.
Ethnic and cultural variations that exist within some countries, such as the vast differences among states in the United States and India, must also be considered.
Visualizing Population Composition with Population Pyramids
Population pyramid: A graph that shows the age-sex distribution of a given population
Projections and trends revealed in population pyramids predict what goods and services are needed, such as schools, elder care, and health care, and what to plan for in the future.
Countries with rapid population growth have a large-based and narrow-topped population pyramid, indicating a high child dependency ratio.
This shape can also signify a peripheral country as it results from high birth rates that supply increasingly more people into the lowest bars of the pyramid and in turn shrink the relative number of people in the oldest stages.
As the death rate declines, more people survive to reproductive ages and beyond.
As these people reproduce, the pyramid base widens.
Peripheral and semi-peripheral countries that have experienced improvements in life expectancy but continue to have high birth rates tend to have this shape.
The pattern reflects a history of rapid population growth and the potential for future rapid growth.
The narrow top is the result of a smaller number of births for many years in the past (when the population was much smaller) and higher death rates at older ages.
