MD

Population Notes: Unit 1 — Comprehensive Study Notes

Unit 1: Population

  • Population: the collection of living organisms in each geographic area.
  • Population Distribution: pattern of human settlement – Where are people settling?
  • Population Density: average population per square mile/km – How crowded is one space?
  • Key historical question: Where have humans settled throughout history?

Population Distribution and Density

  • World population by region shows milestones labeled as 7 billion, 6 billion, 5 billion, 4 billion, 3 billion, 2 billion, 1 billion, 0, with years such as 1820, 1850, 1900, 1950, and 2000–2019.
  • Sources: HYDE (2016) & UN (2019); Regions listed include Oceania, Latin America, North America, Europe, Africa, Asia.
  • Visualization available at Our World in Data (world-population-growth). CC BY.

The Most Populous Nations on Earth

  • Estimated population by country (in millions) in 2003 and 2023*:
    • India
    • China
    • USA
    • Indonesia
    • Pakistan
    • Nigeria
    • Brazil
    • Bangladesh
    • Russia
    • Mexico
    • Ethiopia
    • Japan
  • For 2023, two highlighted values (in millions):
    • India: 1{,}428.6
    • China: 1{,}425.7
  • The slide notes these are middle-range future estimates as of July 1 of the respective years.
  • Source: UN Population Division. Additional sources referenced: Statista, World Population Review.

What should I get from this?

  • US expansion westward correlated with new territory acquisition and exploration of more land.

Population Density: Desirability of land & historical trends

  • Population distribution has remained broadly patterned, but density has increased significantly over time.
  • Why density increased: humans cluster on desirable land while total land area remains relatively constant.

What makes land desirable? Physical vs. Human factors

  • Physical factors: midlatitudes, low-lying areas, access to fresh water and other resources.
  • Human factors: safety/work opportunities, family/friends networks, transportation networks, political stability, culture.
  • Example contrasts:
    • Death Valley-like regions: harsh climates → sparsely populated.
    • Tokyo: densely populated due to mild climate plus economic and political development.

Types of Population Density

  • Arithmetic Density: D_A = rac{P}{A}
    • Definition: population divided by total area.
    • Use: gauge how many people live in an area.
  • Physiological Density: DP = rac{P}{A{arable}}
    • Definition: population divided by land suitable for farming.
    • Use: assess carrying capacity for agriculture.
  • Agricultural Density: D{Ag} = rac{F}{A{arable}}
    • Definition: number of farmers divided by arable land.
    • Use: measure farming efficiency.

Population Composition

  • Understanding population composition helps explain a region’s past, present, and future.
  • Demographic characteristics include: ethnicity, language, religion, age, sex.
  • These characteristics influence regional, national, or state-level planning and policy.

Age–Sex Composition & Population Pyramids

  • Population Pyramid: a graph showing the age–sex distribution of a country’s population.
  • How to read:
    • Age cohorts are displayed along the vertical axis.
    • Sex is shown on the left and right sides (usually male on one side, female on the other).
    • The x-axis represents the percentage of the population.
  • Common term: cohort = a group of people born in the same time period (e.g., males aged 0–4).

Reading a Population Pyramid

  • Key components:
    • Age on the y-axis.
    • Sex distribution along the sides.
    • Percent of population on the x-axis.

Types of Population Pyramids & Stages

  • Pyramids illustrate population change through five stages as a country modernizes.
  • As modernization progresses, the shape of the pyramid changes reflecting birth and death rates.

Common Patterns in Population Pyramids

  • Asymmetry in the upper portion often indicates female longevity (women live longer).
  • Sudden changes reflect events such as wars, natural disasters, epidemics, government interference, or migration.
  • Baby Boom: rapid increase in births following a period of lower births.
  • Baby Bust: lower birth rates following a baby boom.

Anomalies in Population Pyramids

  • Examples of pyramid features and possible reasons:
    • Taller bars for ages 18–25: could indicate a large university town.
    • Taller bars for ages 25–50: may reflect families with school-aged children affected by school funding.
    • Taller bars for ages >65: retirees attracted by warm climates or better living conditions.
    • Taller bars for males: possible occupational age structures or migration patterns (e.g., jobs in mining/oil).
  • These correspondences help interpret demographic shocks and policy effects.

Dependency Ratio

  • Definition: Dependency Ratio = \frac{Dependent\ Age\ Group}{Working\ Age\ Population} \times 100
  • Dependent Age Group: under 15 and over 65.
  • Working Population: ages 15–64.
  • Higher dependency ratio means more dependents relative to earners, implying higher tax burdens and greater pressure on social support systems.

Section 2: Population Growth and Decline

Measuring Births & Deaths

  • Crude Birth Rate (CBR): births per 1000 people.
  • Total Fertility Rate (TFR): average number of children born per woman (childbearing age: 15–49).
  • Crude Death Rate (CDR): deaths per 1000 people.

Births & Deaths as Drivers of Population Change

  • If Birth Rates are higher than Death Rates, population grows.
  • If Death Rates are higher than Birth Rates, population declines.
  • If Birth Rates and Death Rates are similar, population is stable.

Birth Rate (CBR) 2020

  • Definition: live births occurring during the year per 1000 people.
  • Source: Our World in Data; UN Population Division (2019 Revision).
  • Note: Data visualization shows a range of birth rates across countries; some data may be missing for certain regions.

Crude Death Rate (CDR) 2020

  • Definition: annual deaths per 1,000 people.
  • Source: World Bank data visualization; geographic variation shown (no data in some regions).

Changes in Fertility

  • Total Fertility Rate (TFR) tends to decline as countries gain wealth.
  • Historical trend: higher TFR in the past; 1800 milestone: world population reaches 1 billion.
  • Industrial Revolution effects:
    • Pre-1800: Most people lived on farms; higher child labor contributed to higher fertility.
    • Post-1800s: Machines reduce the need for child labor; thus fertility declines.
  • This shift is central to the Demographic Transition Model (DTM).

Other factors influencing TFR

  • Women’s role in society.
  • Availability and education about family planning.
  • Government programs and policies.

Government Programs & Fertility Policy

  • Pro-Natalist: policies that encourage births (e.g., paid maternity leave, subsidized child care).
  • Anti-Natalist: policies that discourage births (e.g., birth control education, incentives to limit family size).
  • Examples:
    • Pro-Natalist: US tax incentives for having children (influence on birth rates).
    • Anti-Natalist: China’s One-Child Policy; European birth control education programs.

Warm-Up Questions (Practice)

  • 1) Is the US tax incentive for having children Pro-Natalist or Anti-Natalist?
  • 2) Is federal access to free family planning clinics and birth control Pro-Natalist or Anti-Natalist?
  • 3) If birth rate < death rate, what is the population trend?

Global Trends in Fertility & Life Expectancy

  • Global TFR has decreased, yet population continues to grow due to other factors.
  • Primary driver of continued growth: rise in life expectancy (average years a person will live).
  • Other life expectancy influencers:
    • Reduction in infant mortality.
    • Improvements in food production and nutrition.
    • Advances in sanitation and health care.
  • Consequently, even with lower fertility, aging populations emerge.

Hans Rosling: Population Growth

  • Resource: Hans Rosling’s works on population dynamics (e.g., Don’t Panic video and related questions).
  • Links provided: YouTube videos and discussion materials used for classroom activities on population growth.

From Pyramids to the Demographic Transition Model (DTM)

  • Population pyramids reflect stages of the DTM.
  • Modernization is associated with changes in fertility and mortality rates.
  • The DTM represents modernization as population composition shifts over time.

Demographic Transition Model (DTM)

  • Visual: a chart with Birth Rate and Death Rate across Stages 1–4, with an optional Stage 5.
  • Concept: stages correspond to how births and deaths change as countries develop.
  • Typical ordering of stages: Stage 1 (High Stationary) → Stage 2 (Early Expanding) → Stage 3 (Late Expanding) → Stage 4 (Low Stationary) → Stage 5 (Declining, debated).

Stage 1: High Stationary

  • No modern country remains fully in Stage 1; examples include isolated groups (e.g., Sentinelese, some Amazonian tribes).
  • Characteristics:
    • High CBR and high CDR; low population growth.
    • Population structure: very young.
  • Reasons:
    • CBR: need for farming labor.
    • CDR: disease and poor sanitation.

Stage 2: Early Expanding

  • High CBR with rapidly declining CDR (due to improvements in nutrition, sanitation, medicine).
  • Result: rapid population growth; population structure very young.
  • Examples: Mali, South Sudan.

Stage 3: Late Expanding

  • CBR and CDR both decline (CBR remains higher than CDR for a period).
  • Population growth remains rapid but slows over time.
  • Population structure: young with rising life expectancy.
  • Examples: Turkey, Indonesia, Mexico.

Stage 4: Low Stationary

  • CBR and CDR both low.
  • Population growth is slow/near zero; age structure becomes balanced and aging.
  • Population examples: United States, China.

Stage 5: Declining? (Contested)

  • CBR and CDR both low, but CBR falls below CDR.
  • Very low or negative population growth; population becomes very old.
  • Examples: Japan, Germany.

Common Patterns & Limitations of DTM

  • Common notes:
    • Stage 2 or 3: some regions lack resources to educate all children.
    • Stage 4 or 5: aging populations strain healthcare funding.
  • Limitations:
    • Does not account for immigration/emigration rates.
    • Government policies (Pro- or Anti-Natalist) can alter trajectories.
    • Not every country fits neatly into a single stage; some move back and forth between stages.
    • No country today is in Stage 1.

DTM Resources & Visuals

  • Links to YouTube videos and other classroom resources for dynamic demonstration of DTM stages.

Malthusian Theory

  • Thomas Malthus (1798): Population growth could outpace agricultural output, leading toward mass starvation.
  • Core idea: unchecked population growth would outstrip resource growth.

Criticisms of Malthusian Theory (Early critiques)

  • Modern evidence shows slower population growth than Malthus predicted due to:
    • Contraceptives and family planning.
    • Education and increased societal roles for women.
  • Graph excerpt (Age 25–29 with Bachelor's degree by sex, 1967–2015) illustrates rising female education levels, correlated with fertility decline.

Modern Rebuttals & Neo-Malthusian Theory

  • Neo-Malthusian perspective: contemporary conditions intensify the resource depletion and environmental risks associated with population growth.
  • Arguments include potential depletion of nonrenewable resources, pollution, food shortages, and broader social/environmental consequences.

Overpopulation & Carrying Capacity

  • Overpopulation occurs when the population exceeds the carrying capacity of a region.
  • Carrying Capacity: the maximum population that a place can physically hold or support given available resources.
  • Visual reference: the idea of running on empty when essential resources (fossil fuels, wilderness, fisheries, water resources) are strained.

Populations, Distribution, Density & Carrying Capacity: Causes & Effects

  • Population distribution and density determine where pressure on land and resources is greatest.
  • Carrying capacity varies by location and resource availability.
  • Causes of overpopulation include resource depletion, migration patterns (e.g., brain drain), disease spread, and reliance on trade.
  • Effects can include resource scarcity, environmental degradation, and economic strain.

Additional Resources

  • Hans Rosling: Population Growth (video resources and discussion questions referenced in class).
  • Useful links and activity prompts provided for deeper exploration of population dynamics and overpopulation.
  • Documented prompts and activities: Hans Rosling: Population Growth Video Questions; Don’t Panic videos and related classroom activities.