Demography Overview

Demography

/

• Demography is the scientific study of human populations, focusing on their growth, decline, and movement.

• Demographers study population dynamics.

• Demography is both a distinct field and a subfield within sociology.

• The term comes from Greek words: "demos" (population) and "graphia" (description or writing).

• Demography studies:

  • Size

  • Composition

  • Distribution of human populations

  • Changes resulting from fertility, mortality, and migration

Key Terms in Demography

• Demography studies determinants and consequences of population change, influencing and being influenced by:

  • Population size: Number of people in a given place.

  • Population growth or decline: How the number of people changes over time.

  • Population processes: Fertility, mortality, and migration trends affecting population size and change.

    • Captures life’s three main moments: hatching, matching, and dispatching.

  • Population spatial distribution: Where people are located and why.

  • Population structure: Number of males and females of each age.

  • Population characteristics: Attributes like education, income, occupation, family relationships, immigrant status, etc.

• Demography connects individual experiences to larger demographic frameworks.

• It considers these experiences at an aggregate level rather than individually.

Population

• Population: Collection of persons alive at a specific time meeting certain criteria.

• Alternatively, the number of people in a specified geographic area.

• Demography describes population characteristics, not individual members.

Population Size: Absolute Size, Distribution, and Density

• Population size has three facets:

  • Absolute size: Has its own consequences.

    • E.g., large classes require different teaching methods.

    • Large cities face different problems than small villages.

  • Distribution (relative size): Also has consequences.

    • E.g., less-developed countries worry about premature urbanization.

  • Density: Number of people in an area relative to its size.

    • It is an average or estimate, often calculated as people per square kilometer.

• Formula for population density: Dp = N ÷ A

  • Dp is the density of the population.

  • N is the total population.

  • A is the land area covered by that population.

• Example: Edmonton, Canada, in 2011:

  • Population: N = 812,200

  • Land area: A = 700 square kilometers

  • Dp = 812220 ÷ 700 = 1160.3 per square kilometer

• Large size and uneven distribution can lead to crowded populations.

• Density Consequences:

  • Negative: Crowds, noise, environmental pollution.

    • Overpopulation reflects concerns about dense populations.

    • Epidemic diseases spread more easily.

  • Positive: Innovation, knowledge, and ideas spread quickly.

Composition

• Demographers compare numbers, focusing on relative category sizes.

• Percentage distribution and ratios are used.

• Traits for classifying population composition:

  • Characteristics that don't change easily (sex, age, ethnicity) are more useful.

  • Traits related to altering population size (birth, death, migration).

  • Age and sex are important due to their relation to biology.

    • E.g., increasing age correlates with a higher chance of dying.

    • College students approaching ages for having children.

    • Women's experiences shaped by childbearing.

• Governments focus on the economic welfare of populations and workforces.

  • Collect information on economic composition.

  • Identify vulnerable groups with special policy needs.

• Public focuses on identifiable subgroups within the nation.

  • National censuses cover ethnic identity, race, religion, national origin, and language.

Population Change

• Demography focuses on studying population change, including changes in size.

• The future population is what we anticipate and plan for.

Population Growth and its Components

• Population growth: Changes in population size.

  • Calculated by subtracting an earlier population count from a later one (P2 – P1).

  • Can be positive or negative.

• Immediate causes of population growth:

  • Births increase population.

  • Deaths decrease population.

• Closed Population:

  • Population where people cannot enter or leave.

    • Changes only through births and deaths.

    • Equation: P2 – P1 = B(1,2) – D(1,2)

      • Population change equals births minus deaths.

      • Difference is called natural increase.

    • Population growth equals natural increase (B – D).

• Open Population:

  • Population where people can enter or leave.

  • Four ways to change population:

    • Births increase population.

    • Deaths decrease population.

    • Immigration increases population.

    • Emigration decreases population.

  • Equation: P2 – P1 = B(1,2) – D(1,2) + M(1,2)

    • Population change equals births minus deaths plus net migration.

    • Net migration is the imbalance between movers-in and movers-out.

    • Can be positive or negative.

  • Even with negative natural increase, substantial net migration can cause growth.

Growth Components as Population Processes

• Population events: Births, deaths, and moves across borders.

• Demographers view these as expressions of collective processes:

  • Births reflect collective fertility.

  • Deaths represent collective mortality.

  • Border crossings indicate migration.

• Crude Rate: Simplest measure of a population process.

• General formula for crude rates: E ÷ Pm × n

  • E = Number of events (births, deaths, etc.).

  • Pm = Estimated total midyear population.

  • n = Base number (e.g., 1,000).

• Multiply by a base number to express the rate per n people.

  • Common practice: Multiply by 1,000 (events per 1,000 people).

• Adjust base to minimize decimals or adjust for events occurring in small fractions of the population.

• 'Crude' Term Intention:

  • Not everyone is equally at risk of dying, giving birth, or migrating.

  • Crude rates provide a quick measure of demographic processes.

• Growth equation can be written in terms of crude rates.

• \frac{P2 − P1}{Pm} = \frac{B(1,2)}{Pm} − \frac{D(1,2)}{Pm} + \frac{M(1,2)}{Pm}

• Each term becomes a crude rate.

• Growth rate = birth rate – death rate + net migration rate.

Population Change: Growth and Reclassification

• Demographers study population composition changes.

• All four components of population growth affect category or subpopulation size.

• Category growth influenced by reclassification (migration of meaning among subpopulations).

• Reclassification Examples:

  • Catholics choosing not to baptize children.

  • Others converting to Catholicism.

• Reclassification difficulty varies by trait:

  • Sex: Changes limited.

  • Age: Proceeds predictably.

  • Occupation: Individual choices with no simple pattern.

• Study of changing subpopulation composition is a prominent topic across social sciences.

• Nuptiality (changing marital status) is a special focus:

  • Affects growth processes.

  • Implies a jointly functioning social unit.

  • Couples viewed differently by governments.

  • Data systems gather evidence about union formation.

Summary

• Demography = study of population size, composition, processes that change it, and relationships with the broader environment.

• Formal demography: Emphasizes demographic variables and their interrelationships.

• Population studies: Includes non-demographic determinants and consequences of demographic variables.

• Demography analyzes dynamic processes by which populations change.

• Growth equation is a fundamental feature.

• Population events seen as manifestations of population processes.

• Demographers use rates to measure force of these processes.

• Population composition changes determined by fertility, mortality, migration, and reclassification.

Population Analysis

• Demography: Scientific study of human population dynamics.

• Emerged about 150 years ago as nations began keeping population statistics.

• Governed by births, deaths, and migrations.

• Often treated as a branch of sociology due to social and cultural nature of these factors.

• Relies on statistical analysis, large-sample surveys, and official records.

• Censuses: Systematic surveys conducted by virtually all countries to gather basic population statistics.

• Not 100% accurate and may not adequately represent every individual.

• Decennial census in the United States mandated by the Constitution.

• Some individuals (undocumented immigrants, homeless) may not be counted.

• Demographic statistics may be unreliable in countries of the Global South.

Basic Concepts in Demography

• Crude Birthrates:

  • Number of live births per year per 1,000 persons in the entire population.

  • Called “crude” because they don't focus on women of childbearing age.

  • Useful for overall comparisons.

  • Global crude birthrate in 2019: 19 per 1,000.

  • US: much lower at 13 per 1,000.

  • Germany and Italy: 9 per 1,000.

  • Japan: 8 per 1,000.

  • India: 18 per 1,000.

  • Many African nations: Exceeded 40 per 1,000.

  • Highest rates in Angola, Niger, and Mali: 44 per 1,000.

  • Low-income countries: 35 per 1,000 (more than three times that of high-income countries).

  • Global crude birthrate has declined from 36 per 1,000 in 1963 to 19 per 1,000 today.

• Fertility:

  • Number of live-born children the average woman has.

  • Social and cultural factors play a role.

  • Fertility rate calculated as average births per 1,000 women of childbearing age.

• Crude Death Rates (Mortality Rates):

  • Number of deaths per 1,000 people in the population per year.

  • Significant variations among countries.

  • Global crude death rate in 2019: 8 per 1,000.

  • US: slightly higher at 9 per 1,000.

  • India and China: slightly lower at 7 per 1,000.

  • Highest rates in Bulgaria, Lesotho, and Serbia: 15 to 16 per 1,000.

  • High rates result from poverty, poor healthcare, HIV/AIDS, warfare, drugs, and natural disasters.

  • Global crude death rates have fallen from 18 per 1,000 in 1960 to 8 per 1,000 today.

• Crude death rates provide a general index of mortality and can be misleading.

• Do not account for the age structure of a country.

  • European Union: 10 per 1,000.

  • Middle East and North Africa: 5 per 1,000.

  • Europe has four times as many people over 65 compared to the Middle East and North Africa.

• Infant Mortality Rate:

  • Number of babies per 1,000 births who die before reaching the age of one.

  • Significant factor in the population explosion has been the reduction of infant mortality rates.

  • 2018: 29 babies per 1,000 births worldwide died in infancy.

  • Ranges from 1 to 2 per 1,000 in Norway, Sweden, and Finland to 85 in the Central African Republic.

  • US: 6 per 1,000.

  • Cuba: 4 per 1,000, prioritizing preventive medicine.

• Life Expectancy:

  • Influence on increasing life expectancy.

  • Number of years the average person can expect to live.

  • 1900, US: about 40 years.

  • Today: nearly 79 years.

  • After surviving the first year of life in 1900, the average life expectancy was 58 years.

  • Influenced by illness, nutrition, and natural disasters.

  • Life span is the maximum number of years an individual can live.

  • Only a small proportion of people live to be 100 or more.

Dynamics of Population Change

• Measured by subtracting the yearly number of deaths per 1,000 from the number of births per 1,000.

• Accounts for migration (immigration and emigration).

• 1.1 percent increase each year globally, half the rate from 50 years ago.

• Population growth is exponential.

• People born today add to the total population, creating a larger base for future growth.

  • Approximately 7.7 billion people in the world today.

  • Annual growth rate is 1.1 percent.

  • Next year there will be 84.7 million more people (7,700,000,000 × 1.1 percent = 84,700,000), bringing the total to 7,784,700,000.

  • Each year, the number of people added increases.

• Doubling time: Measured using the doubling time—the period required for the population to double.

• Formula to calculate doubling time: 70 ÷ current growth rate

• Population growing at 1 percent will double in 70 years.

• 2 percent growth rate will double the population in 35 years.

• 3 percent growth rate in 23 years.

• Industrialized countries have growth rates of less than 0.6 percent.

• European Union in 2018: 0.2 percent (doubling in 350 years).

• United States: 0.6 percent (doubling in 117 years).

• Some countries have experienced population decline due to war or economic collapse (Syria and Venezuela).

• Japan, Portugal, and Italy (all with –0.2 percent growth).

• Economic success correlates with declining population growth.

• Poorest countries have the highest crude birthrates and thus the fastest-growing populations.

• Low-income countries grew by 2.6 percent in 2018, meaning their populations will double in just 27 years.

• High birthrates result in youthful populations.

• 42 percent of people in low-income countries are under 14 years old, compared to only 17 percent in high-income countries.

• Niger: half the population is under 14.

• A young, impoverished population poses numerous social and economic challenges.

• Educational opportunities are often scarce.

• Many children forced to work full time, while others live as street children.

• Large numbers of unemployed or underemployed young people can create unrest.

• Poor countries consume far less than rich countries (smaller environmental impact).

• Their rapidly growing populations require additional resources.

• Industrialization may result in slower population growth in the long run.

The Demographic Transition

• Successful industrialization and economic development in Europe and the United States led to slower population growth.

• Demographic transition: Concept first proposed by Warren S. Thompson in 1929.

• A three-stage process where one form of population stability is replaced by another.

• Stage one:

  • Typical of pre-industrial societies.

  • High birthrates and death rates.

  • Infant mortality rates are especially high.

  • Minimal population growth because the high number of births is offset by a similarly high number of deaths.

  • Periods of population increase were often followed by increases in death rates.

• Stage two:

  • Began with the onset of industrial development in Europe and the United States in the early 19th century.

  • Death rates decline while fertility remains high.

  • The decline in death rates is due to improved agriculture and advances in public health and sanitation systems and medical knowledge.

  • Fertility rates remain high at first due to cultural lag.

  • Results in significant population growth.

• Stage three:

  • Cultural norms shift from favoring high birthrates to favoring low birthrates.

  • Birthrates and death rates realign—this time at low levels—leading to a stable population.

  • Economics of raising children changes.

  • Parents no longer require many children to help on farms.

  • Child labor was made illegal, and compulsory schooling meant parents had to support their children.

  • Children viewed as an economic cost rather than an economic asset.

  • Parents began prioritizing “child quality” over “child quantity”.

  • Industrial development brought technologies that allowed women to control their fertility.

  • Number of children a woman had came to be seen as a matter of personal choice.

  • Women achieve higher levels of education and higher earnings in the labor market, the incentive to have fewer children increases.

  • Higher education among both men and women is also linked to delayed marriage and childbearing.

• Demographers debate on how to interpret these changes or how long stage three will last.

• Fertility in Western countries has not remained completely stable.

• Nonetheless, this sequence is generally accepted as describing a major transformation in the demographic characteristics of modern societies.

• Second Demographic Transition:

  • Demographers have debated whether a “second demographic transition” has begun in the most developed industrial countries.

  • Fertility rates continue to decline due to shifts in family structure.

  • Influences include delayed marriage, delayed childbearing, increasing rates of cohabitation, high and steady rates of divorce, and easier access to effective birth control.

  • These factors may lead to lower birthrates, as many people may prefer not to have children.

  • Some societies seem to have entered a fourth stage, in which birthrates decline below replacement levels, leading to population decline.

  • Has been observed in many European countries, as well as in Japan and Singapore.

  • Aging population, where the proportion of young people decreases while the proportion of elderly individuals rises significantly.

  • Could have widespread economic and social implications for developed countries if this trend continues.

  • Dependency ratio: Increase in the dependency ratio—the ratio of economically dependent individuals to economically active individuals.

  • As the dependency ratio rises, there will be increasing pressure on health care and social services.

Glossary

• Demography – the study of populations.

• Crude birthrates – statistical measures representing the number of births within a given population per year, normally calculated in terms of the number of births per 1,000 members.

• Age-specific birthrates – statistical measures representing the number of births within a given population per year in relation to age distribution.

• Fertility – the average number of live-born children produced by women of childbearing age in a particular society.

• Crude death rates – statistical measures representing the number of deaths that occur annually in a given population, normally calculated as the ratio of deaths per 1,000 members. Crude death rates give a general indication of the mortality levels of a community or society, but they are limited in their usefulness because they do not take into account the age distribution.

• Mortality – the number of deaths in a population.

• Infant mortality rate – the number of infants who die during the first year of life, per 1,000 live births.

• Life expectancy – the number of years the average person can expect to live.

• Rates of population growth or decline – a measurement of population change calculated by subtracting the yearly number of deaths per 1,000 from the number of births per 1,000.

• Exponential – a geometric, rather than linear, rate of progression; producing a fast rise in the numbers of a population experiencing such growth.

• Demographic transition – a theory that shows how birth and death rates are related to stages of industrial development, with high birth and death rates transitioning to low birth and death rates as a country transitions from a pre-industrial to an industrialized economy.

• Second demographic transition – a new demographic model that calls for fertility rates that may continue to fall because of shifts in family structure.

• Dependency ratio – the ratio of people of dependent ages (children and the older population) to people of economically active ages.