1112010 Dr Salwa Tayel Demography 1 DEMOGRAPHY By
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DEMOGRAPHY By Dr. Salwa Tayel Associate Professor Family and Community Medicine Department King Saud University 1/11/2010 Dr. Salwa Tayel Demography 2
Learning objectives By the end of this lecture you will be able to: n Define demography n List elements of demography n Describe population pyramids n Compare between population pyramids of developed and developing countries. 1/11/2010 Dr. Salwa Tayel Demography 3
DEMOGRAPHY v. Demography is the science that studies human population. Demography v. 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. 1/11/2010 Dr. Salwa Tayel Demography 4
Elements of Demography: Three main elements: 1 - Size of population (census) 2 - Composition 3 - Distribution 1/11/2010 Dr. Salwa Tayel Demography 5
Population Census n The population size is determined by counting the inhabitants and their characteristics periodically. n This census is of importance for each country for planning purposes and is usually done every 10 years. n Sex, age, nationality, religion, occupation, marital status, level of education, economic characteristics etc. are investigated in the census. 1/11/2010 Dr. Salwa Tayel Demography 6
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. 1/11/2010 Dr. Salwa Tayel Demography 7
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. 1/11/2010 Dr. Salwa Tayel Demography 8
Demographic indicators for the year 2005 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 1/11/2010 Dr. Salwa Tayel Demography 9
Population Pyramids 1/11/2010 Dr. Salwa Tayel Demography 10
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. 1/11/2010 Dr. Salwa Tayel Demography 11
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United States Population, 1995 19 Source: Joseph A. Mc. Falls, Jr. Population: 1/11/2010 A Lively Dr. Salwa Tayel Demography Introduction. Population Bulletin 46(2); 1995: 22.
Factors affecting population Pyramids Factors that influence population include: n Fertility (births), n Mortality (deaths) and n Migration. 1/11/2010 Dr. Salwa Tayel Demography 20
Structure Of Population Pyramids n n n Sex n Males are shown on the left side of the pyramid n Females on the right Age n young persons at the bottom, and n 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. 1/11/2010 Dr. Salwa Tayel Demography 21
Bases for Comparison: 1) 2) Variation across age groups Variations within each age group by sex 1/11/2010 Dr. Salwa Tayel Demography 22
From the shape of the pyramid the following can be learnt: 1. Sex ratio: Percentage of males and females. 2. Age structure: n Base denotes births (broad or narrow base) n Apex denotes elderly 3. Mortality and emigration: Shape of sides (sloping or steep). 4. Life expectancy: Height of the pyramid and shape of the apex. 1/11/2010 Dr. Salwa Tayel Demography 23
From the shape of the pyramid the following can be learnt: 5. 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. 1/11/2010 Dr. Salwa Tayel Demography 24
6. Dependency Ratio n The Dependency Ratio describes the relation between n the potentially self-supporting portion of the population and n the dependent portions at the extreme of age. 1/11/2010 Dr. Salwa Tayel Demography 25
Types of Dependency Ratio n n n 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 1/11/2010 Dr. Salwa Tayel Demography 26
Dependency ratio 1/11/2010 Dr. Salwa Tayel Demography 27
Items Developing country Developed country …………………. . …………………… 2 - The sides. …………………… 3 - The height. ……………………. . ……… …………… 5 - The dependency ratio (DR) …………………… a) The young DR. …………………… b) The old DR. …………………………… …………… 1 - The base. 4 - The median age (High or low). 28 c) The total DR. Dr. Salwa Tayel Demography 1/11/2010
Bibliotheca Alexandrina Thank you salwatayel@hotmail. com Website http: //faculty. ksu. edu. sa/73234/default. aspx 1/11/2010 24/10/2010 Dr. Salwa Tayel (Descriptive Studies) Dr. Salwa Tayel Demography 29 29
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