Lecture 7 Population Dynamics

Slide 1:

Population Distribution, Dynamics and Migration

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Objectives Define demography, birth/death/fertility rates, population density, demographic transition, mobility and migration Talk about why we care… Learn about population pyramids

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So Why do We Care?

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Demography Study of the characteristics of human populations Areal distribution of earth’s population Consequences of this distribution at multiple scales Census: count of people in a nation, region, city Used to apportion legislative seats Used to redistribute taxes to fund schools, hospitals, other public institutions Vital records: Births, deaths, marriages

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World Population Density

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Population per Physician

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Birth/fertility Rates Ratio of the number of live births in a single year for every 1000 people in a population (crude birth rate) Might be different for different groups within a population Age, race Total fertility rate: number of children born to a woman between the ages of 15-49 Usually countries with low birth rates, have low death rates as well Total fertility rate: measure of the number of children a woman will have over her lifetime

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Fertility Rates

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Death/mortality rates Number of deaths per year per 1000 people Also varies within a population Health care availability, social class, occupation, place of residence Infant mortality rate: annual number of deaths of infants less than one year of age compared to total number of births that same year Life expectancy: average number of years an infant is expected to live Also varies by race, class, gender

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Death Rates

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Life Expectancy

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Population Growth Natural increase: difference between CBR and CDR Population doubling time: amount of time it will take for a population to double 1.8 %--current rate Will double in 40 years

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Population Growth Rates

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Age-Sex Pyramids

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Population Pyramids

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Population Pyramids

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Demographic Transition Phase 1: High birth and death rates, low natural increase, low total population Phase 2: High birth rate, lowering death rate, high natural increase, population growth Phase 3: Falling birth rates and low death rates, high natural increase, population growth Phase 4: Low birth and death rates, low natural increase, high total population

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Food and Population Sustaining world population with food Thomas Malthus (British demographer: 1766-1834) Food supply increases arithmetically, while human population increases geometrically We’ll run out of food eventually He was wrong…so far Hunger is a socio-political problem, not an agricultural problem

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Limits to Population Growth Limit population growth Restrict fertility Education of women Delay pregnancy Work=security Wealth=retirement Non-agricultural occupations Choice

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Mobility Mobility: ability to move from one place to another Migration: long distance move to a new location Immigration: moving to a particular location Emigration: moving from a particular location

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Push/Pull Factors Push factors-reasons to leave (emigrate) Political unrest/persecution Lack of jobs Disasters Pull factors-reasons to arrive (immigrate) Reunification with families Economic opportunities Freedom from persecution

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Migration Voluntary migration: job opportunities International: across country borders Internal: within a country Forced migration: refugees, deportees International: across country borders Internal: within a country

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Migration International forced—refugees, deportees International voluntary—economic migrants, “knowledge “migrants Internal forced—internally displaced persons Internal voluntary—migrant workers, “snowbirds”

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Involuntary Migration, Aghanistan

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Involuntary Internal Migration, US

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Voluntary Internal Migration, US

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Population Growth

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Alcohol Consumption (Litres/capita/year)

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Miniature Earth