Population Geography & Demographics Study Notes

Spatial Distribution & Environmental Factors

Uneven Distribution Patterns: Population is heavily concentrated in specific global regions, with Eurasia housing 69.2% of the world's population.
National Disparities:
- In Russia, 147 million people live in the European section (<25% of land area), while Siberia (Asian part) accounts for only 23% of total population.
- In the United States, population has shifted from northern and midwestern Snow Belt states toward coastal areas and southern/southwestern Sunbelt states (California to Florida). The mean center of U.S. population moved west for 130 years and steadily southwest since 1920, reaching Plato, Missouri in 2010.
- In Utah (13th largest state by area), around 80% of its 3.1 million people (2017) live in and around Salt Lake City.

Physical Influences:
- Elevation: Lower elevations are preferred in mid-to-high latitudes to avoid cold temperatures. In tropical regions (e.g., South America), populations concentrate at higher elevations (>3,000 feet / 900 meters in the Andes) to escape hot climates and disease.
- Bodies of Water: Concentrations are dense along ocean coasts (e.g., half of Australia's population resides in 5 port cities).
- Climate: Extremely cold or dry areas (e.g., Australia's "dead heart" desert interior) support only sparse populations.

Population Pyramids & Structural Patterns

Structure: Bar charts showing 5-year age cohorts with males on the left and females on the right.

Population pyramids for selected countries and communities

- Four Typical Shapes:

- **Rapid Growth**: Wide base reflecting high birth rates (e.g., Tanzania).

- **Slow Growth**: Gently tapering base (e.g., United States).

- **Stability**: Column/pillar shape with equal cohort sizes.

- **Decline**: Narrow base / top-heavy structure (e.g., Spain).

Atypical Pyramids:
- Migrant Worker Bulge: Extreme male bulge in middle cohorts (e.g., Oman, Qatar).
- Retirement Community: Top-heavy age distribution (e.g., Sun City, Arizona, restricted to ages 55+).
- Suburban Families: Dual bulges in young children and middle-aged adults (e.g., Overland Park, Kansas).
- College Town: Large bulge in 18–24 cohort (e.g., Lawrence, Kansas, home to University of Kansas).

Impacts & Consequences of Population Distribution

Economic Development: High density reduces per-person infrastructure costs (roads, utilities, public transit) and attracts private market investments.
Political Impact: Shifts in population dictate legislative representation. In the U.S., 435 House of Representatives seats (averaging 710,767 people per seat) are reapportioned every 10 years; between 2000 and 2010, 8 states gained 12 seats due to Sunbelt growth.
Environmental Impact: Densely populated urban centers suffer from elevated air pollution (e.g., smog in Los Angeles) and habitat destruction.

- Human Well-Being & Health: High density does not inherently diminish quality of life (e.g., Monaco is the most densely populated nation yet has high income per capita and life expectancy). However, dense settlement accelerates infectious disease transmission (e.g., malaria in urban African centers) and heightens vulnerability to natural disasters.

Population Dynamics & Growth Trends

Demographic Equation: Determines total population change over a specific period. $\text{End Population} = \text{Beginning Population} + \text{Total Births} + \text{Total In-migrants} - \text{Total Deaths} - \text{Total Out-migrants}$

Diagram of the basic demographic equation

- Historical Population Milestones:

- Agriculture origin (11,000 years ago): 5–10 million people.

- Year 1 C.E.: A few hundred million people.

- 1804: 1 billion.

- 1930: 2 billion (126 years to double).

- 1974: 4 billion (44 years to double).

- 1987: 5 billion.

- 1999: 6 billion.

- October 30, 2011: 7 billion (symbolized by Danica Camacho in Manila, Philippines).

- Early 2020: 7.76 billion (projections: 9.8 billion by 2050; 11.2 billion by 2100).

- Out of \~107 billion Homo sapiens ever lived, \~7.8 billion are alive today.

World population growth projections from 1700 to 2100

### Demographic Rates & Calculations

Crude Birth Rate (CBR): Annual live births per 1,000 people.
- Formula: $\text{CBR} = \left(\frac{\text{Total Live Births}}{\text{Total Mid-Year Population}}\right) \times 1000$
- World average (2018): 19 per 1,000 (More-developed: 10; Less-developed: 21; Least-developed: 33).
- Categories: Low (10–20 per 1,000), Transitional (20–30 per 1,000), High (>30 per 1,000).

Total Fertility Rate (TFR): Average number of children a woman bears in her lifetime (ages 15–49).
- Replacement Level Fertility: TFR of 2.1 stabilizes a population over time.
- World average: 2.4 (or 2.5 in regional figures). Sub-Saharan Africa average is 4.6 (Niger highest at 7.2). Europe average is 1.6 (Bulgaria at 1.6 expects 28% population decline by 2050). Lowest worldwide: South Korea, Puerto Rico, Singapore, San Marino (1.0–1.1).

- Crude Death Rate (CDR): Annual deaths per 1,000 people.

- Formula:  $\text{CDR} = \left(\frac{\text{Total Deaths}}{\text{Total Mid-Year Population}}\right) \times 1000$ 

- World average (2018): 7 per 1,000. More-developed countries average higher CDR (10 per 1,000; EU average 10; Bulgaria 16; Latvia 15) due to older population structures compared to less-developed countries (7 per 1,000) or Persian Gulf states (1–2 per 1,000).

Infant Mortality Rate (IMR): Deaths of infants under 1 year of age per 1,000 live births.
- Global average: 31 per 1,000 live births. Developed countries are <5; developing countries reach 50–70.

Rate of Natural Increase (RNI): Percentage population growth excluding migration.
- Formula: $\text{RNI} = \frac{\text{CBR} - \text{CDR}}{10}$
- China (2018): CBR 12, CDR 7 $\rightarrow \text{RNI} = 0.5\%$
- Nigeria (2018): CBR 39, CDR 12 $\rightarrow \text{RNI} = 2.7\%$

Rule of 70 (Doubling Time): $\text{Doubling Time (Years)} = \frac{70}{\text{Growth Rate (\%)}}$
- Nigeria doubling time: $70 \div 2.6 = 27\text{ years}$ .

Fertility & Mortality Influences

Economic Factors: Agricultural economies demand larger families for manual labor; urban/industrialized nations feature lower fertility due to high child-rearing costs and access to contraceptives.
Socio-Cultural Factors: Religions like Catholicism and Islam encourage large families, though exceptions exist (e.g., Italy and Spain have TFRs of 1.3).
Education & Gender Roles: Higher female educational attainment and workforce participation decrease family size ("more books, fewer babies").
Government Policies: Anti-natalist policies (e.g., China's birth control policies resulting in TFR 1.8) lower fertility; pro-natalist policies offer financial incentives to raise birth rates.
Disease Effects: Historical pandemics (Black Death killed 75–200 million; 1918 Spanish flu killed 50 million, including 5% of India's population) drastically altered populations. Animal diseases like nagana (sleeping sickness spread by tsetse flies in East Africa) decimate cattle and induce human migrations.

Population Composition & Age Structure

Age Cohorts: Pre-reproductive (0–14 years), reproductive (15–49 years), post-reproductive (50+ years).
- Sub-Saharan Africa: 41% of the population is under 15 (Niger reaches 49.3%).
- Germany: 21% of the population is over the retirement age of 65.

Dependency Ratios: Measures burden on working-age individuals (ages 15–64).
- Youth Dependency Ratio: Dependents under 15 per 100 working-age individuals.
- Elderly Dependency Ratio: Dependents aged 65+ per 100 working-age individuals.

Social Generations in the United States

GI Generation: Born before 1924; lived through the Great Depression and fought in World War II.
Silent Generation: Born 1924–1945; grew up during Great Depression and WWII, fought in Korean War, valued frugality and social stability.
Baby Boomers: Born 1946–1964; post-WWII spike in birth rates yielding 72 million members in the U.S.
Generation X: Born 1965–1980; 64 million members in 2018.
Millennials (Generation Y): Born 1981–2000; 83 million members (largest U.S. generation), highly educated but impacted by the 2007–2009 Great Recession.
Generation Z (Centennials / iGen): Born after 2000; hyper-connected via mobile technology.

Sex Ratio Dynamics & Imbalances

Natural Ratio: Naturally occurring biological ratio at birth is 105 boys to 100 girls (or 95 girls to 100 boys).
Androcentrism & Cultural Preference: Preferences for male heirs lead to female infanticide or sex-selective abortions.
- China (2016): 87 girls per 100 boys (most skewed globally).
- India (2016): 89 girls per 100 boys (overall sex ratio 107.48 males per 100 females in 2019).
- Manitoba study: Indian-born women with two daughters were twice as likely to have a son third ( $192\text{ males}:100\text{ females}$ ).

Gender-Selective Migration: Male-dominated industries skew local ratios.
- Mining/Oil towns: Williston, North Dakota saw a 74% population increase (2010–2017) dominated by young males aged 20–40. Alaska had 107 males per 100 females in 2016.
- Persian Gulf states (Saudi Arabia, UAE) import large numbers of male manual workers.

Consequences: Severe male surplus leads to increased human and sex trafficking (e.g., trafficking of women into India from Nepal and Myanmar).

Measures of Population Density

Arithmetic (Crude) Density: Average number of people per unit of total land area.
- Formula: $\text{Arithmetic Density} = \frac{\text{Total Population}}{\text{Total Land Area}}$
- Global average (2018): 133 persons/sq mi (51 persons/sq km) based on 7,621 million people over 57.51 million sq mi (148.94 million sq km).
- Regional extreme examples: Australia has 8 persons/sq mi (3/sq km), whereas Bangladesh has 2,927 persons/sq mi (1,130/sq km).

Physiological Density: Average number of people per unit of arable land. Reflects population pressure on agricultural land.
- Formula: $\text{Physiological Density} = \frac{\text{Total Population}}{\text{Arable Land Area}}$
- Japan: Arithmetic density is 867 persons/sq mi (335/sq km), but physiological density reaches 7,409 persons/sq mi due to only 11.7% (17,074.51 sq mi out of 145,936 sq mi) being arable.
- Egypt: Arithmetic density is 249 persons/sq mi, while physiological density is 8,881 persons/sq mi (<3% arable land).
- United States: Physiological density is 550 persons/sq mi.

Agricultural Density: Number of farmers per unit of arable land. Measures agricultural labor intensity.
- Formula: $\text{Agricultural Density} = \frac{\text{Total Farm Population}}{\text{Arable Land Area}}$
- India (2015): 442 farmers/sq mi (171/sq km) with 272.82 million agricultural workers over 616,605 sq mi of arable land.
- United States (2012): Just over 5 farmers/sq mi (2/sq km) with 3.18 million farmers over 587,889 sq mi of arable land.
- Japan (2016): 114 farmers/sq mi (44/sq km) with 1.92 million agricultural workers.