1. Dr. Salwa Tayel Demography
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2. Family and Community Medicine Department
DEMOGRAPHY By
Dr. Salwa Tayel
Associate Professor
Family and Community Medicine Department
King Saud University
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3. Dr. Salwa Tayel Demography
Learning objectives
By the end of this lecture you will be able to:
Define demography
List elements of demography
Describe population pyramids
Compare between population pyramids of developed and developing countries.
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4. Dr. Salwa Tayel Demography
Demography is the science that studies human population.
Demography:
Is the statistical study of the characteristics of human populations, especially with reference to size and density, growth, distribution, migration and vital statistics, and the effect of all these on social and economic conditions.
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Elements of Demography:
Three main elements: 1- Size of population (census) 2- Composition 3- Distribution
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Population Census
The population size is determined by counting the inhabitants and their characteristics periodically.
This census is of importance for each country for planning purposes and is usually done every 10 years.
Sex, age, nationality, religion, occupation, marital status, level of education, economic characteristics etc. are investigated in the census.
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Types of Census:
A. De Facto Enumeration:
Counting all people in the locality where they are present at the time of the census irrespective of the person’s usual residence.
De Facto census is
economic procedure and
much simpler
But, moving people can be counted twice
It is adopted in the majority of countries.
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Types of Census:
B . De Jure Enumeration:
Counting all people of locality according to their actual residence regardless of their actual location during census time.
Expensive
More difficult and takes time
adopted in U.S.A.
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9. Dr. Salwa Tayel Demography
Demographic indicators for the year Census: 23,118,994 Saudis: 16,854,154 Non Saudis: 6,264,840 Crude Birth Rate: 25.3/1000 population Crude Death Rate: 3.8/1000 population
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Population Pyramids
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11. POPULATION PYRAMIDS: THE AGE-SEX COMPOSTION OF POPULATIONS
Population pyramid is the graphical presentation of the age and sex composition of a population of an area or country at a point in time.
The shape of the pyramid reflects the major influences of births and deaths, in addition to any changes due to migration.
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19. United States Population, 1995
Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Population Bulletin 46(2); 1995: 22.
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20. Factors affecting population Pyramids
Factors that influence population include:
Fertility (births),
Mortality (deaths) and
Migration.
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21. Structure Of Population Pyramids
Sex
Males are shown on the left side of the pyramid
Females on the right
Age
young persons at the bottom, and
the elderly at the top.
The pyramid consists of a series of bars, each drawn proportionately to represent the percentage contribution of each age – sex group
(often in five-year groupings) to the total population
The total area of the bars represents 100 per cent of the population.
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Bases for Comparison:
Variation across age groups
Variations within each age group by sex
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23. From the shape of the pyramid the following can be learnt:
Sex ratio: Percentage of males and females.
Age structure:
Base denotes births (broad or narrow base)
Apex denotes elderly
Mortality and emigration: Shape of sides (sloping or steep).
Life expectancy: Height of the pyramid and shape of the apex.
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24. From the shape of the pyramid the following can be learnt:
Median Age: (lower or higher)
The point in the vertical axis of age through which passes the horizontal line that divides the surface area of the pyramid into two equal parts (50%) younger and 50% older).
The position of this defined point is inversely related to the width of the base.
The wider the base, (i.e. the higher the birth rate), the lower the median age and vice versa.
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6. Dependency Ratio
The Dependency Ratio describes the relation between
the potentially self-supporting portion of the population and
the dependent portions at the extreme of age.
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26. Types of Dependency Ratio
Young dependency: Presented by the surface area below the horizontal line passing through 15 years of age.
Old dependency: Presented by the surface area above the horizontal line passing through 65 years of age.
Total dependency: Presented by the surface area below the horizontal line passing through 15 years of age and that above the horizontal line passing through 65 years of age
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Dependency ratio
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28. Dr. Salwa Tayel Demography
Developed country
Developing country
Items
…………………..
1-     The base.
……………………
2-     The sides.
3-     The height.
……………………..……………………
4-     The median age (High or low).
5-     The dependency ratio (DR)
a)     The young DR.
b)     The old DR.
…………………………………………
c)      The total DR.
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29. Thank you salwatayel@hotmail.com
Bibliotheca Alexandrina
Thank you
Website
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Dr. Salwa Tayel (Descriptive Studies) 29
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