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The Dynamics of Demography
Demography is the scientific study of population.
 Sociologists study population because it affects
social structure, especially in crowded areas.
 The collection of population data is very important
because of its use by government and industry.
 Sociologists look for patterns that will help them
understand and predict how groups of people will
behave.
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How do sociologists define population?
A population is a group of people living in a
particular place at a specified time.
 To study population, demographers look at many
factors, including size, distribution, composition,
and structure.
 Demographers analyze three processes: birth,
death, and migration.
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How is fertility measured?
Fertility is measured in several ways.
 The crude birth rate is the annual number of live
births per one thousand members of a population.
 The fertility rate is the annual number of live
births per one thousand women aged fifteen to
forty-four.
 The total fertility rate is the average number of
children born to a woman during her lifetime.
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Mortality
Mortality refers to the number of deaths within a
population.
 Sociologists analyze mortality by examining life
span and life expectancy.
 Sociologists measure mortality by analyzing the
crude death rate and the infant mortality rate.
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Migration
Migration refers to the movement of people.
 It can occur within a country or between countries.
 Sociologists measure migration using the gross
migration rate or net migration rate.
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World Population
World population growth exhibits certain patterns.
 Countries measure
the number of people
in a population by
taking a census.
 The world’s
population continues
to grow at a rapid
rate, since the
doubling time is
getting shorter.
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Malthus and Population Growth
In 1798, Thomas Robert Malthus, an English
minister and economist, published An Essay on the
Principle of Population. He described relationships
between population growth and economic
development.
 Population, if left unchecked, will exceed the food
supply.
 Checks on population can be positive (increase
mortality) or preventative (decrease fertility).
 For the poor, any improvement in income is eaten
up in additional births.
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 The wealthy and well-educated already exercise
preventive checks.
The Demographic Transition
The demographic transition theory states that
population growth is a function of the level of
economic development in a country.
 This theory takes into account agricultural
productivity and reliable methods of birth control.
 Demographic transition theory describes four
stages of population growth.
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Future World Population Growth
World population growth has reached a turning
point. After more than two hundred years of
increase, the annual population growth rate is
declining. Despite this decline, world population will
continue to grow until the middle of the twenty-first
century.
 Zero population growth will occur when deaths
are balanced by births so that the population does
not increase.
 Population momentum is the inability to stop
population growth immediately due to a previous
high rate of growth.
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Future World Population Growth
 The replacement level is the rate at which people
replace themselves without adding to the
population.
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Population Control
Population control is the conscious attempt to
regulate population size through national birth
control programs.
 By 1990, most countries had in place formal
programs to reduce birth rates.
 The voluntary use of population control methods is
generally known as family planning, and it has a
mixed success rate.
 Compulsory methods of family planning have been
instituted by some governments and achieved
high success rates.
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Population Pyramids
Population pyramids are a graphic depiction of the
age and sex composition of a population.
 Age and sex are key indexes of fertility and
mortality rates.
 Population pyramids
illustrate the
dependency ratio
that relates the
number of
dependent persons
and economically
active persons.
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The Urban Transition
 The first preindustrial cities developed in fertile
areas where surplus food could be grown.
 With the Industrial Revolution came a major
increase in the rate of urbanization.
 The development of factories was an especially
important influence on the location of cities.
 Urbanization in developed and developing nations
has occurred at different speeds.
 The United States is now primarily a suburban
nation.
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Urbanization
 A city is a dense and permanent concentration
of people living in a limited geographic area who
earn their living primarily through nonagricultural
activities.
 The world has been greatly changed by
urbanization–the process by which an increasingly
larger portion of the world’s population lives in or
very near to cities.
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World Urbanization
Urbanization is a worldwide movement. Nearly 45
percent of the world’s population now lives in urban
areas.
 Developed and developing countries have
distinctly different patterns of urbanization.
 The number and size of cities differs between
developed and developing nations.
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Suburbanization in the United States
Suburbanization occurs when central cities lose
population to the surrounding areas.
 The United States is now predominantly suburban.
 Since 1950, the proportion of the population living
in suburbs has more than doubled.
 Technological developments have caused
suburbanization.
 Cultural and economic pressures have also
encouraged the development of suburbs.
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What is the central city dilemma?
The central-city dilemma is the concentration of a
large population in need of public services without the
tax base to provide them.
 Businesses followed the more affluent people to
the suburbs because of lower tax rates, less
expensive land, less congestion, and a new
customer base.
 One solution to the central-city dilemma is
gentrification–the restoration of parts of inner
cities.
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What are edge cities?
An edge city is a suburban unit specializing in a
particular economic activity. It is a small, morefocused version of an urban downtown.
 Employment may focus on a particular industry,
such as computer technology, finance, or health
care.
 Edge cities offer a full range of services.
 Edge cities are not separated from the larger
urban area by legal and physical boundaries.
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Urban Ecology
Urban ecology is the study of the relationships
between humans and their city environments.
 Although every city is unique, patterns have been
found in the way humans interact with the cities
they inhabit.
 Urban ecologists have developed four major
theories of city growth: concentric zone theory,
sector theory, multiple nuclei theory, and
peripheral theory.
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of city growth or click the right arrow to proceed through the presentation.
Concentric Zone Theory
Concentric zone theory describes city growth in
terms of distinctive zones that develop from the
central city outward in a circular pattern.
 The central business district is the innermost circle
and the heart of the city.
 The zone in transition is the zone that surrounds
the central business district.
 The three zones that surround the central
business in consecutive order are the zone of
workingmen’s homes, a residential zone, and the
commuters’ zone.
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Sector Theory
Sociologist Homer Hoyt advocated the sector theory
that said growth patterns are strongly affected by
major transportation routes.
 Sectors tend to be pie-shaped, with wedges
radiating from the central business district to the
city’s outskirts.
 Some sectors will be predominantly industrial,
others will contain stores and professional offices,
others will be “neon strips” with motels and fastfood restaurants, and still others will be residential
sectors, each with its own social class and ethnic
composition.
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Multiple Nuclei Theory
Chauncy Harris and Edward Ullman suggested that
cities do not always follow a pattern dependent on a
central district, and they developed the multiple
nuclei theory.
 The multiple nuclei theory states that a city may
have several separate centers, some devoted to
manufacturing, some to retail trade, some to
residential use, and so on.
 These specialized centers can develop because of
the availability of automobiles and highways.
 They reflect such factors as geography, history,
and tradition.
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Peripheral Theory
The peripheral theory emphasizes the growth of
suburbs around the central city.
 Many cities today no longer have a central city
core to which other parts of the metropolitan area
are oriented all of the time.
 Dependence on shipping, railroads, and heavy
manufacturing has been replaced by more flexible
means of transportation, such as cars and trucks,
and large urban areas are now encircled by
highways.
 New technologies are also loosening the ties of
most parts of the city to the central city core.
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