Population Basics Demographics

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Population BasicsDemographics

• In order to save this file to the website, many
  visual illustrations had to be eliminated to
  reduce the file size.

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Part I Population Distributions
Distribution describes the locations on the
Earths surface where individuals or groups live.
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Distribution of Population

• World population is most dense in 4 regions
• East Asia
• South Asia
• Southeast Asia
• Western Europe

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Sparsely Populated Areas

• Wet Lands
• Dry Lands
• Cold Lands
• High Lands

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Ecumene

• The portion of the earth with permanent human
  settlement, has expanded to cover most of the
  worlds land area.

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Ecumene Over Time
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Part II Population Density

• Density is a measurement of the number of people
  per unit area such as a square kilometer or
  square mile.
• How is Density different from Distribution?

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Types of Density

• Arithmetic Population Density the total number
  of people per a unit of land area.
• Physiological Density the total number of people
  per a unit of arable (farmable) land.
• Agricultural Density The total rural population
  / amount of agricultural land.

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Part II Measures of Population
ChangePopulation Change refers to any given
shift in the overall makeup of a given population
usually referring to either positive population
growthor negative population growth
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Major Population Measures

• Crude Birth Rate (CBR)
• Crude Death Rate (CDR)
• Natural Increase Rate (NIR)
• Total Fertility Rate (TFR)
• Infant Mortality Rate (IMR)

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Population Measures

• Crude Birth Rate
• Total number of births in a year for every 1,000
  people alive in a society
• Crude Death Rate
• Total number of deaths in a year for every 1,000
  people alive in a society

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Natural Increase Rate

• The percentage growth of a population in a year,
  computed as the crude birth rate minus the crude
  death rate
• The worlds NIR is about 1.3 percent or 80
  million people per year
• At current rates the world population will double
  again in 54 years Doubling Time
• Almost all of the worlds natural increase is
  centered in less developed countries
• What parts of the world are growing most quickly?
  Slowly?

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Fertility

• Total Fertility Rate (TFR) is used to measure the
  number of births in a society.
• This is the average number of births a woman will
  have through her child-bearing years (15 through
  49)
• The average world TFR is 3, though it exceeds six
  in some African countries and is less than 2 in
  Europe Replacement Rate

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Infant Mortality

• Infant Mortality Rate (IMR) is the annual number
  of deaths of infants under one year of age
  compared to total live births per 1000.
• Life expectancy measures the number of years a
  newborn child can expect to live
• Babies born today in Western Europe can be
  expected to live into their late 70s, early 30s
  in Africa
• CBR, NIR, TFR and IMR can all be used as
  predictors of a countrys development

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Calculating Infant Mortality
Survivorship curves keep track of the fate of any
given birth cohort. They show the percent still
living at a given age.
Upper curve Late 20th.C. developed country.
Middle Curve 19th. C. developed country/20th.C.
less developed country. Lower Curve City of
York (England), 16-17th.C.
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Illustrating Population

• Population Pyramid A bar chart that shows the
  age and sex distribution of members of a 
  population. The age divisions are referred to as
  "cohorts" and may be in 5 or 10 year increments,
  depending on the level of detail desired. By
  convention, females are always plotted to the
  right, males to the left. The units across the
  base may be either absolute numbers or percent of
  the population.

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Illustrating Population Change over Time The
Demographic Transition Model

• The "Demographic Transition" is a model that
  describes population change over time. It  is
  based on an interpretation begun in 1929 by the
  American demographer Warren Thompson, of the
  observed changes, or transitions, in birth and
  death rates in industrialized societies over the
  past two hundred years or so.
• By "model" we mean that it is an idealized,
  composite picture of population change in these
  countries. The model is a generalization that
  applies to these countries as a group and may not
  accurately describe all individual cases. Whether
  or not it applies to less developed societies
  today remains to be seen.

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• STAGE ONE  is associated with pre Modern times,
  and is characterized by a balance between birth
  rates and death rates. This situation was true of
  all human populations up until the late 18th.C.
  when the balance was broken in western Europe.
• Note that, in this stage, birth and death rates
  are both very high (30-50 per thousand). Their
  approximate balance results in only very slow
  population growth. Over much of pre-history, at
  least since the "Agricultural Revolution" 10,000
  years ago, population growth was extremely slow.
  Growth rates would have been less than 0.05,
  resulting in long doubling times of the order of
  1-5,000 yrs.  

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• STAGE TWO sees a rise in population caused by a
  decline in the death rate while the birth rate
  remains high, or perhaps even rises slightly. The
  decline in the death rate in Europe began in the
  late 18th.C. in northwestern Europe and spread
  over the next 100 years to the south end east.
• The decline in the death rate is due initially to
  two factors improvements in food supply and
  significant improvements in public health that
  reduced mortality, particularly in childhood

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• STAGE THREE  moves the population towards
  stability through a decline in the birth rate.
  This shift belies Malthus's belief that changes
  in the death rates were the primary cause of
  population change.

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• STAGE FOUR is characterized by stability. In this
  stage the population age structure has become
  older

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A Population at Stage 4
Birth Rate 12 per thousand Total fertility
rate 1.8 births Natural increase 0.1 per year
1990-2000 Age structure 18 under 15 yrs.age
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Extreme Stage 4In some cases the fertility rate
falls well below replacement and population
decline sets in rapidly
Birth Rate 9 per thousand Total fertility rate
1.2 births Natural increase -0.1 per year
1990-2000 Age structure 14 under 15 yrs.age
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Population Momentum

• Population momentum refers to the  tendency for
  population growth to continue beyond the time
  that replacement-level fertility has been
  achieved because of a highly relatively high
  concentration of people in the childbearing
  years.
• Look at the following pop. pyramids of India at
  three different time periods and note the
  changes.

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• By using these concepts we can then explain the
  differences we see in population growth rates
  across the world today