Chapter 4: Demography

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Chapter 4 Demography

• aka Population Studies or Population Science
• The study of human populations
• Size
• Composition
• Distribution
• Causes and consequences of changes in those
  characteristics

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Demography is interdisciplinary

• Many factors impact population
• Demographers can be trained in
• Sociology
• Economics
• Biology
• Geography
• History
• Health sciences
• ANTHROPOLOGY

3
Population measures

• Fertility
• Mortality
• Migration

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Fertility

• Number of births that occur to an individual or
  in a population
• Worldwide fertility ranges from 1.3 in Spain to
  7.4 in Niger
• US fertility is approx. 2.1
• Hutterite fertility was 12

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Fecundity

• Physiological ability to have children
• Fecundity ranges from 0-30 in females to
  0-infinity in males
• Factors which limit reproduction
• Cultural
• Social
• Economic
• Epidemiological

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Intermediate variables affecting fertility

• Davis and Blake 1956 Fecundity
• Ability to have intercourse, conceive, and carry
  to term
• Sexual unions
• Formation and dissolution, age at first
  intercourse, proportion of women in unions, time
  spent outside a union, coital frequency,
  celibacy, temporary separations
• Birth control
• Contraceptive use, sterilization, abortion

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Industrialized countries

• Contraceptive use and abortion most important
  factors

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Developing countries

• Infecundity due to STDs, HIV/AIDS, lactational
  amenoreah (Interbirth interval), and postpartum
  abstinence (postpartum taboo) most important
  factors

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Fertility patterns

• This implies that people in industrialized
  countries want to limit their fertility and
  people in developing countries are limited by
  exogenous factors

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Measures of fertility

• Period rates
• Cohort rates

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Period rates

• Total fertility rate (TFR)
• Average number of children born per women in a
  population
• Replacement level fertility
• Fertility required to keep a population at its
  current level
• Crude birth rate (CBR)
• Number of births per 1000 population
• General fertility rate (GFR)
• Number of births per woman
• Net reproductive rate (R0)
• Current births plus expected births (RV)

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Period rates contd.

• Most of these measures focus on women 15-49 years
  old. Why?

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Cohort rates

• Completed fertility rate (CFR) or completed
  family size (CFS)
• Number of live births to a woman who has
  completed reproduction (menopause)

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Variation in fertility

• Within a society or political entity
• Between a society or political entity
• Between men and women in the same society

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Mortality Death

• Usually measured as
• Crude death rate number of deaths per 1,000
  population
• Worldwide range from 2 in the Persian Gulf states
  to 30 in civil war torn Sierra Leone
• n US about 9 per 1,000

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Death rate

• Highly influence by age-structure of the
  population.
• Where a higher percentage of the population is
  older, death rates tend to be higher
• What about the effect of HIV/AIDS in relation to
  the age-specific death rate?

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Life Expectancy

• Number of years members of an age class can
  expect to live based on the current death rates
  of older age classes
• Often misused, is a period rate like TFR also
  constructed from a life table (sum of
  age-specific death rates)
• Not to be confused with life span
• The maximum human life span now seems to be in
  the 120s. Few people, however, live to be 100

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Variation in mortality

• Age
• Sex
• Socioeconomic status

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Migration

• Movement of people into or out of a specific
  geographic area
• Most variable of the agents of demographic change
• Difficult to measure due to lack of reporting and
  monitoring

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Types of migration

• In-migration (immigration)
• Out-migration (emigration)
• International vs. internal

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Net migration

• Difference between in- and out-migration

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Variation in migration

• Age
• Young adults, life cycle changes
• Gender
• In Africa males migrate, in much of Asia and
  Latin America females migrate
• Education
• Extremesboth very poor and very wealthy migrate
• Socioeconomic status
• Depends on the type of job

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International migrants

• Major destinations for immigrants
• US, Australia, Canada, European Community, Israel
• Often motivated by economic hardship, war,
  political instability
• Chain migration
• Choice of destination determined by presence of
  social or kin network

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Variation in international migration

• Age
• Young adults
• Gender
• Same as for internal migration
• Education
• Educated, often professionals
• Socioeconomic status
• Higher than those who stay behind

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Population size and growth

• Rate of natural increase
• Crude birth rate minus crude death rate
• In USA (1997) this was 14.6-8.66.0 (0.6)
• Worldwide this was 23.1-9.014.0 (1.4)
• Growth rate
• Rate of natural increasenet migration
• A growth rate of 1 means a population will
  double in 70 years

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At present growth rates

• Worlds population will double in 50 years
• If the growth rate doubles to 2.8, the worlds
  population will double in 25 years
• Conversely if the growth rate decreases by half
  to 0.7, the doubling would occur in 100 years

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Demographic balancing equation

• Shows the roles of fertility, mortality, and
  migration in population change
• Population Birthsdeaths immigrants-emigrants
• Used in population projection

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Population projection

• Demographers can project population based on
  current rates of fertility, mortality, and
  migration
• Also can use estimated future rates
• Projections lose accuracy quickly as the
  projected time increases since it is difficult to
  know how demographic characters will be affected
  by variables in the future
• US hit 300,000,000 on Tuesday at 730am

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Population composition

• The aggregation of individual demographic
  characteristics on a population level
• Population pyramids
• Age sex composition
• Four shapes
• Pyramidalhigh growth
• Rectangularslow growth
• Ovaldecline
• HourglassAIDS driven decline
• US Census International Population Pyramid
  Projections

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Other components

• Sex
• Race
• Ethnicity

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Race

• Race as a classification has come under great
  fire
• There may be a genetic or biological component to
  race, but in general it is a subjective
  classification which varies greatly depending on
  time and place.
• For instance, slaves in the US could have only
  one-sixteenth African ancestry
• Today in the US this subjective classification
  continues

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Race may be useful

• It gives us some idea of who might be subject to
  discrimination
• Ethnicity refers to linguistic and/or cultural
  heritage and should not be confused with race

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Population distribution

• Worldwide population distribution is shifting to
  developing countries due to higher fertility
• Both in the USA and worldwide, urbanization is a
  critical influence on population distribution

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How many people can the earth support?

• Carrying capacity of the eartharound 10 billion
  (Cohen 1995)
• When will the earth reach 10 billion at current
  rates of growth?
• Around 2035

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Demographic Transitions

• Three types of demographic transitions
• Fertility
• Mortality
• Health (also called Epidemiologic)

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Why are demographic transitions important?

• The combined effect of demographic transitions
  results in very low population growth
• The age structure of the population becomes older
• This has effects on economy, health institutions,
  educational institutions

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Geopolitics

• Most international population policy oriented
  towards slowing population growth has focused on
  inducing fertility transition
• This would lower fertility and slow population
  growth to some extent
• Reversing mortality and health transitions is not
  ethically or politically viable

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Theories of fertility transitions

• Classical demographic theory
• Economic models
• Social models
• Evolutionary models

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Classical transition theory

• Industrialization and modernization led to
  initial higher fertility due to improved health
  care and higher quality and more reliable food
  supply
• Because pre-industrial societies had high
  mortality, higher fertility was necessary for
  those societies to survive
• Fertility could only be expected to fall due to
  the effects of industrialization higher
  survival, individualism, consumerism, mobile
  urban populations, lessening of familial ties,
  and decline of fatalism

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Classical transition theory contd.

• Three phases of fertility decline
• Inicipient decline--widespread fertility control,
  heavy industrialization
• Transitional growth--low mortality but high
  fertility, industrializing
• High growth potentialhigh mortality and high
  fertility, very low industrialization

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Economic explanations

• Applied principles of microeconomics to
  childrenanother normal good
• Differ in whether desire for children is
  established early in life or is based on current
  conditions
• Supply and demand Children are more in demand
  where they are less expensive
• Economic value of children depends on context of
  subsistence economy.

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Social explanations

• Post-modernist interpretation
• Ideational change is major motivator of fertility
  transitions
• Uses diffusion theory
• Ideas about the number of children to have follow
  linguistic boundaries and diffuse from elites and
  centers of power to the hinterlands

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Evolutionary perspectives

• Humans like other organisms evolved in the
  context of fitness maximization
• Maximizing genetic representation in succeeding
  generations
• Human lifestyles vary widely and may show great
  divergence from the lifestyle in which human
  reproductive psychology evolved
• We can still understand reproductive behavior in
  the present as the manifestation of evolved
  psychological mechanisms

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These perspectives differ in two related aspects

• Theory of motivation
• Are people motivated by the uptake of culturally
  specific roles or by their self-interest?
• Acquisition and utilization of information
• Do people pattern their fertility after some
  cultural norm or is fertility a response to
  environmental/economic conditions?

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Cost/value of children

• Biologists (Trivers), demographers (Caldwell),
  and economists (Becker) have all independently
  recognized that offsprings ability to provision
  themselves are important factors in determining
  parental fertility

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Agriculture

• Cultivation and herd animals
• Domestication
• Occurred worldwide about 12,000 years ago
• Mesopotamia
• Levant
• China
• Indus valley
• Mesoamerica

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Effects of agriculture

• Agriculture changes time allocation in relation
  to subsistence pattern
• Affects all age-sex groups
• Leads to effects of sedentization
• Changes diet composition
• Increase in simple carbohydrates such as starch
  and sugar
• Increased use of animal fat
• Use of dairy products
• Potential serious consequences in micronutrient
  balance

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Epidemiological transition

• Increasing health issues related to agriculture
  and sedentism
• Diet led to vitamin/mineral deficiency in some
  places due to heavy reliance on one staple grain

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Epidemiological transition cont.

• Dental problems
• Due to malnutrition
• Due to soft food and sweeteners
• Due to grit from grain processing
• Dental damage from grit and sugar
• Repetitive stress injury
• Difference in agricultural tasks
• More consistent food supply in most places

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Demographic transition

• Agriculture appears to be related to substantial
  increases in fertility and possible decreases in
  mortality
• Fertility change is due partly to diet change but
  also is strongly related to changes in time
  allocation and the benefits of sedentism

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Social consequences

• Population concentration
• Storage of resources
• Power differentials
• All led to complex societies
• Cities
• Social stratification

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Transition

• Nomadic hunter gatherers subsisted on widely
  varied diet including grasses, fruits, roots and
  tubers, mammals, birds, and fish
• Small groups used seasonal camps
• Population density 2-3 person/square mile

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Transition cont.

• Maize agriculture was introduced before 1050
• Evidence
• Broken hoes
• Maize in refuse heaps
• Large settlements
• Largest had 1000 permanent inhabitants
• Continual occupation
• Population density increased to 25 persons/square
  mile

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What happens if you only eat corn?

• Maize has very low levels of the amino acid
  lysine
• Relying heavily on maize leads to niacin
  deficiency called pellagra
• Pellagra has afflicted many maize eating
  populations including Southerners in the US
  during the depression in the 1930s

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How to avoid pellagra

• Native Americans in what is now Mexico treated
  maize with lime water or fire ash water
• This releases tryptophan from the maize which the
  body can utilize in the production of niacin
• Hopi Indians roasted maize which liberates niacin
• Others harvested maize when it was immature and
  contained more niacin
• People who did not know to do this and relied on
  maize suffered from pellagra

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How did people learn this?
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Reliance on a staple

• Nutritional problems
• Susceptibility to starvation
• Crop disease
• Drought

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Degenerative conditions

• Osteoarthritis of articular surfaces of joints
  and vertebral column
• 40 of hunter-gatherer adults
• 70 horticultural adults
• Repetitive stress injury?

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Child growth and development

• Horticultural children had decreased rate of
  growth 0-5 years
• Caught up to hunter-gatherer children after age
  10

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Child growth and development cont.

• Dental hypoplasias
• Deficiency in enamel thickness
• Result of physiological stress
• Position on tooth indicates age of stress
• 55 of hunter-gatherers have hypoplasias
• 80 of horticulturalists
• Horticulturalists hypoplasias peak at age 2 ½
• ½ year earlier than hunter-gatherer
• Indicates earlier weaning and reliance on cereals
  as weaning foods
• Continual food shortage??

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Life expectancy

• Hunter-gatherer life expectancy at birth is 26
  years
• For horticulturalist 19 years
• 13 of H-G died at less than 1 year
• 22 of horticulturalist
• 15 year old H-G had 23 more years life expectancy
• 15 year old horticulturalist had 18 more years
  life expectancy