Population Composition & Structure

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Population Composition & Structure


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The most basic elements of population composition areSex structureAge structure


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Sex structureThe most basic measurement is the sex ratio

The number of males per 100 females

Sex ratio = # of males x 100

#of females


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If Sex ratio > 100, there are more males than

femalesSex ratio < 100, there are more females than

malesSex ratio = 100, there are equal #s of both

sexes


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Important factors that affect the sex ratio are:The differences in death rates between

males and femalesThe differences in net migration by genderThe sex ratio of newborn infants


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Sex ratios at birth, 2008World = 107US = 105China = 111Mexico = 105France = 105Mozambique = 104

Source: CIA World Factbook


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Sex ratios change as age progressesMigration is a very significant factor


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Figures in the text, pp. 56-59“Frontier”

Early factorImmigration magnets

More recent

Sex Ratios by County, 2000

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Age StructureAffects economic and social behaviorPrimary determinant

Birth rateAnalysis of age structure

Population pyramids


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Population pyramids5 year age groups or cohortsA cohort is a group of people who share a temporal (time) experienceYouth Middle agedOld agedBaby BoomersGen XersBaby Boomerangs

Post WWII US Baby BoomBorn between 1946-196479 million babies were born 1930s to early 1940s

new births in the US averaged 2.3 - 2.8 million/year

19463.47 million births in the US

Peak in 1957 & 19614.3 million births each year

Source: http://geography.about.com/od/populationgeography/a/babyboom.htm

Source: Wikipedia.com

Number of Births in the US, 1934 to 2000

Baby Boom

Population Pyramids of Rapid, Slow, and Zero Population Growth, 1990

DenmarkUnited StatesKenya


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Analysis of population structure is important becauseFuture patterns of population growthAmongst which age cohortsStructure of dependent population relative to

the working age/productive populationDependency ratio

Dependency Ratio

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Ratio of the dependent-age population (the young and the old) to the working age population

The purpose of the dependency ratio is to measure the # of dependents that each 100 people in the productive years must support

Dependency Ratio

Population Composition & Structure

Technology

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