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Population Composition & Structure
Population Composition & Structure
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The most basic elements of population composition areSex structureAge structure
Population Composition & 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
Population Composition & Structure
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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
Population Composition & Structure
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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
Population Composition & Structure
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Sex ratios at birth, 2008World = 107US = 105China = 111Mexico = 105France = 105Mozambique = 104
Source: CIA World Factbook
Population Composition & Structure
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Sex ratios change as age progressesMigration is a very significant factor
Population Composition & Structure
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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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Population Composition & Structure
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Age StructureAffects economic and social behaviorPrimary determinant
Birth rateAnalysis of age structure
Population pyramids
Population Composition & Structure
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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
Population Composition & Structure
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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