Population Pyramids = graphic device that represents a population

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Population Pyramids graphic device that
represents a populations age and sex composition.

• Pyramid describes diagrams shape for many
  countries in 1800s when was created.

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A broad base of younger age groups and
progressively narrowing to apex as older

• Populations were thinned by death.
• Now there are many different shapes.

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Quickly growing population of Kenya jas ,most
people in lowest age cohorts

• Percentage in older age groups declines
  successively with markedly sloping sides.
• Typically female life expectancy is decreased in
  older cohorts of less developed countries 50
  for Kenya proportion of females in older age
  groups is less than in Sweden or U.S.

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In wealthy countries with very slow rate of
population growth population is nearly equally
divided - so pyramids have

• Almost vertical sides.
• War can be reflected by showing depleted age
  cohorts and male female disparities.
• The of a countrys population in each age group
  strongly influences demand for goods and services
  within that national economy.
• Country with high of young has high demand for
  educational facilities and health delivery
  services.

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Dependency Ratio measure of of dependents
old and young that each 100 people in productive
years (15 64)

• Must support.
• Population Pyramids show this.
• Population pyramids also foretell future problems
  from present population policies or practices.
  Ex. Chinas population policies skewed in favor
  of males.

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Natural Increase Rate of Natural Increase of
population derived by subtracting

• The Crude Death Rate from the Crude Birth Rate.
• Natural means increases or decreases due to
  migration are not included.
• This rate is usually expressed as a or rate per
  100 rather than 1,000.
• Doubling Time Time it takes for population to
  double.

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Ex. 2 rate of increase recorded 1999 by
developing world except China

• Population would double in 35 years since 1
  rate would take 70 years to double.
• Population Doubling Time estimated by dividing
  the Growth Rate into the number 70 ( 70 divided
  2 35 years).
• Globally Rates of Increase have risen over
  history. Thus doubling time has decreased.

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Should world fertility rates decrease - - as have
recently population doubling time

• Will correspondingly increase as it has since
  1990.
• Even small annual additions accumulate to large
  total increments because of geometric or
  exponential (1,2, 4, 8) instead of arithmetic
  growth.
• Inevitable consequences of doubling or J-Curve
  Growth.

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The Demographic Transition some form of braking
mechanism must operate to control totally
unregulated population

• Growth voluntary or involuntary.
• Demographic Transition voluntary relation
  between population growth and economic
  development. traces changing levels of human
  fertility and mortality associated with
  industrialization and urbanization.

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This model assumes over time high birth and
death rates will slowly be replaced by low rates.

• The 1st Stage of process and demographic
  transition model characterized by high birth
  and high but fluctuating death rates. When
  births only slightly exceed deaths the
  population will grow only slowly.
• From 1 AD to 1650 for population to increase
  from 250 million to 500 million Doubling Time
  of over millenium and a half. Offset by
  sometimes catastrophic decline like bubonic
  plague. This 1st Stage no longer found in any
  country.

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This model was developed to explain population
history of Western Europe.

• Western Europe entered 2nd Stage with
  industrialization 1750 its effects declining
  death rates with high birth rates have dispersed
  worldwide without universal industrial economies.
• Rapidly increasing population during 2nd Stage
  results from dramatic increases in life
  expectancy. This reflects falling death rates
  due to advances in medical and sanitation
  practices, rising per capita incomes,
  urbanization that provides environment where
  medicine and food distribution improvements are
  concentrated.

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Birth rates dont fall as soon as death rates
cultural patterns change more slowly than
technologies.

• Many Latin American and South and Southwest Asian
  countries show charcteristics of 2nd Stage.
• Annual rates of increase of these countries are
  near or above 30 per l,000 and their population
  will double in 20 to 25 years. Means
  underdeveloped societies have been beneficiaries
  of life preservation techniques.

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Third Stage when birth rates decline as people
begin to control family size.

• Urban, industrialized societies may view kids as
  economic liabilities, instead of assets as
  agrarian societies do.
• When birth rate falls and death rate remains low
  population size begins to level off.
• 4th Stage End of model final stage
  characterized by very low birth and death rates.
  This results in very slight increases in
  population and doubling times stretching to l,000
  years or more.

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Extension of 4th Stage into 5th Stage
population decrease has so far been confined to
rich, industrialized countries

• Throughout the world Europe and Japan.
• By 2010 most worlds population growth will
  result from Demographic Momentum not 2nd Stage
  expansion.
• Original model made to describe Northwest
  European countries as went from rural-agrarian to
  urban industrial.

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Beginning 1860 lst death rates then birth rates
began gradual decline.

• Mortality Revolution first came as
  epidemiological transition echoed demographic
  transition to which its associated.Many formerly
  fatal epidemic diseases became Endemic
  continual within a population. As people
  developed partial immunities mortalities with
  them declined.

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Health of European population increased with
improving animal husbandry, crop rotation, etc

• Sewage systems, sanitary water supplies common
  in larger cities hygiene improved everywhere.
• Deaths associated with chronic illnesses
  associated with maturing and aging population
  increased.
• Passed to Age of Degenerative and Human-Origin
  Diseases.

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Increases recently in drug and antibiotic
resistant diseases, pesticide resistance

• Of disease-carrying insects, and AIDS cast doubt
  on finality of ultimate stage.
• In Europe decrease in death rates was echoed by
  decreases in birth rates as societies altered
  traditional concepts of ideal family size.