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Family and Community Medicine DepartmentFamily and Community Medicine DepartmentKing Saud UniversityKing Saud University

DEMOGRAPHYDEMOGRAPHY

Learning objectives Learning objectives

Define of demographyDefine of demography

List elements of demographyList elements of demography

Describe population pyramids Describe population pyramids

Compare between population pyramids of Compare between population pyramids of

developed and developing countries.developed and developing countries.

By the end of this lecture you will be able to:By the end of this lecture you will be able to:

DEMOGRAPHYDEMOGRAPHY

DemographyDemography is the science that studies human population.

DemographyDemography::

Is the statistical study of the characteristics of human Is the statistical study of the characteristics of human

populations, especially with reference to populations, especially with reference to sizesize and and densitydensity, ,

growthgrowth, , distributiondistribution, , migrationmigration and and vitalvital statistics, and the statistics, and the

effect of all these on social and economic conditions.effect of all these on social and economic conditions.

Three main elements:Three main elements:

1- Size of population (census) 1- Size of population (census)

2- Composition 2- Composition

3- Distribution3- Distribution

Elements of Elements of Demography:Demography:

Factors affecting populationFactors affecting population

Factors that influence population include:Factors that influence population include: Fertility (Fertility (births),births), Mortality (Mortality (deathsdeaths) and ) and Migration.Migration.

Population CensusPopulation Census The population size is determined by counting the The population size is determined by counting the

inhabitants and their characteristics periodically.inhabitants and their characteristics periodically.

This census is of importance for each country for This census is of importance for each country for

planning purposes and is usually done every 10 planning purposes and is usually done every 10

years. years.

Sex, age, nationality, religion, occupation, marital Sex, age, nationality, religion, occupation, marital

status, level of education, economic characteristics status, level of education, economic characteristics

etc. are investigated in the census.etc. are investigated in the census.

Types of CensusTypes of Census::

A. De Facto Enumeration:A. De Facto Enumeration:

Counting all people in the locality where they are Counting all people in the locality where they are present at the time of the census irrespective present at the time of the census irrespective of the person’s usual residence. of the person’s usual residence.

De Facto census is De Facto census is

economic procedure and economic procedure and

much simpler much simpler

But, moving people can be counted twice But, moving people can be counted twice

It is adopted in the majority of countries.It is adopted in the majority of countries.

B . De Jure Enumeration:B . De Jure Enumeration:

Counting all people of locality according Counting all people of locality according to their actual residence regardless of to their actual residence regardless of their actual location during census their actual location during census time. time.

ExpensiveExpensive

More difficult and takes timeMore difficult and takes time

adopted in U.S.A.adopted in U.S.A.

Types of CensusTypes of Census::

Demographic indicators for the Demographic indicators for the

year 2005 year 2005

Census:Census: 23,118,99423,118,994

Saudis:Saudis: 16,854,15416,854,154

Non Saudis:Non Saudis: 6,264,8406,264,840

Crude Birth Rate:Crude Birth Rate: 25.3/1000 25.3/1000

population population

Crude Death Rate: 3.8/1000 Crude Death Rate: 3.8/1000

populationpopulation

Population PyramidsPopulation Pyramids

POPULATION PYRAMIDS: POPULATION PYRAMIDS:

THE AGE-SEX COMPOSTION OF POPULATIONSTHE AGE-SEX COMPOSTION OF POPULATIONS

Population pyramidPopulation pyramid is the graphical presentation is the graphical presentation

of the age and sex composition of a population of the age and sex composition of a population

of an area or country at a point in time.of an area or country at a point in time.

The shape of the pyramid reflects the major The shape of the pyramid reflects the major

influences on births and deaths, in addition to influences on births and deaths, in addition to

any changes due to migration.any changes due to migration.

Structure Of Population PyramidsStructure Of Population Pyramids

SexSex Males are shown on the left side of the pyramidMales are shown on the left side of the pyramid Females on the right Females on the right

AgeAge young persons at the bottom, and young persons at the bottom, and the elderly at the top. the elderly at the top.

The pyramid consists of a series of bars, each drawn The pyramid consists of a series of bars, each drawn proportionately to represent the percentage contribution of each proportionately to represent the percentage contribution of each age – sex group age – sex group

(often in five-year groupings) to the total population (often in five-year groupings) to the total population The total area of the bars represents 100 per cent of the The total area of the bars represents 100 per cent of the

population.population.

Bases for Comparison:Bases for Comparison:

1)1) Variation across age groupsVariation across age groups

2)2) Variations within each age Variations within each age group by sexgroup by sex

United States Population, United States Population, 19951995

Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Population Bulletin 46(2); 1995: 22.

From the shape of the pyramid the following From the shape of the pyramid the following can be learnt:can be learnt:

1.1. Sex ratio: Percentage of males and females.Sex ratio: Percentage of males and females.

2.2. Age structure:Age structure:

BaseBase denotes births (broad or narrow base) denotes births (broad or narrow base)

Apex denotes elderly Apex denotes elderly

3.3. Mortality and emigration: Shape of Mortality and emigration: Shape of sides (sloping sides (sloping

or steep)or steep)..

4.4. Life expectancy: Life expectancy: HeightHeight of the pyramid and shape of the pyramid and shape

of the of the apex. apex.

From the shape of the pyramid the following From the shape of the pyramid the following can be learnt:can be learnt:

5.5. Median Age: Median Age: (lower or higher)

The point in the vertical axis of age through which passes The point in the vertical axis of age through which passes

the horizontal line that divides the surface area of the the horizontal line that divides the surface area of the

pyramid into two equal parts (50%) younger and 50% pyramid into two equal parts (50%) younger and 50%

older).older).

The position of this defined point is inversely related to the The position of this defined point is inversely related to the

width of the base. width of the base.

The wider the base, (i.e. the higher the birth rate), the lower The wider the base, (i.e. the higher the birth rate), the lower

the median age and vice versa.the median age and vice versa.

6. Dependency Ratio6. Dependency Ratio

The Dependency Ratio describes the The Dependency Ratio describes the

relation between relation between

the potentially self-supporting portion of the potentially self-supporting portion of

the population and the population and

the dependent portions at the extreme of the dependent portions at the extreme of

age.age.

Types of Dependency RatioTypes of Dependency Ratio

Young dependencyYoung dependency: Presented by the surface area : Presented by the surface area below the horizontal line passing through 15 years below the horizontal line passing through 15 years of ageof age..

Old dependencyOld dependency: Presented by the surface area : Presented by the surface area above the horizontal line passing through 65 years above the horizontal line passing through 65 years of ageof age..

Total dependencyTotal dependency: Presented by the surface area : Presented by the surface area below the horizontal line passing through 15 years below the horizontal line passing through 15 years of age and that above the horizontal line passing of age and that above the horizontal line passing through 65 years of agethrough 65 years of age

1006515

6515X

yearsbetweenagedPopulation

yearsabovethoseyearsbelowPopulation

ratiodependencyTotal

1006515

15X

yearsbetweenagedPopulation

yearsbelowPopulation

ratiodependencyYoung

1006515

65.. X

yearsbetweenPopulation

yearsabovePopulationratiodependencyOld

Dependency ratioDependency ratio