Population growth Lecture 4

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Population growth - Lecture 4

• Population growth
• Basic components of growth
• Closed and open populations
• Population growth absolute and relative change,
  rate of change
• Doubling time
• World population growth
• Differential growth
• Important concepts

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Population Growth

• Population change
• Is the change or the difference in the population
  from one point in time to another and it can be
  either negative or positive
• P2 P1 Growth in population
• P1 population at the start
• P2 population at the end

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Population change basic components of growth

• Example Population change Fiji 1986 and 1996
• 775077-715375 59702
• Two basic components of growth
• Natural increase Births - Deaths
• Net migration In-migrants Out-migrants
• P2 - P1(B1-2-D1-2) (I1-2 - O1-2)

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Population Change

• Closed population
• Population characterized by the absence of
  migration
• P2 P1 B-D
• Open population
• Population characterized by migration
• P2 P1 (B-D) (I-O)
• Population change is usually classified into 2
  categories
• Absolute change
• Relative change

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Population Growth

• Absolute change
• Absolute change is obtained by using the
  demographic equation
• P2 - P1(B1-2-D1-2) (I1-2 - O1-2)

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Relative change

• Relative change
• The observed change in numbers divided by the
  number of people at the beginning of the period
  P2-P1 x 100
• P1 1
• Example Population change Fiji 1986 and 1996
• 775077-715375 x 100
• 715375 1

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Rate of population growth

• Rate at which a population is increasing (or
  decreasing) in a given year due to natural
  increase and net migration, expressed as a
  percentage of the base population
• P2 P1ert
• Where
• rthe unknown growth rate t the time interval
  between P1 and P2
• e is a constant (2.71828), base of the natural
  of the logarithm

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Example of computing exponential growth rate

• Exponential growth rate r ?
• P1 775,160 (1996)
• P2 1,046,357 (2016)
• n 20 years (1996-2016)
• r ln (P2/P1)/n
• r ln 1.349859384/20 0.15 or 1.5

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How fast can populations grow

• Population can grow exponentially the same way
  money grows in a savings account when an interest
  is paid and not withdrawn
• 100 50 men and 50 women
• 50 women have 2 girls and 2 boys each
  200children.
• 100 females became mothers with 4 children 400
  children
• At the end of 25 years from the original 100
  people, add their 200 children and their 400
  grandchildren equal 700 people

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Doubling Time

• Annual growth rates are translated into years to
  double at that rate
• Years to double 70/ annual growth rate
• Doubling time is a device for dramatizing the
  implications of growth rates if extended over time

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Doubling Time

• Population doubling time is useful to demonstrate
  the long term effect of a growth rate
• Doubling time example
• Fiji 1986-1996 tdouble 70/0.9 77 years

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Growth rates around the world

• Region Growth rate Doubling time
• 
  
  Years
• World 1.5 47
• Africa 2.7
• Asia 1.5 47
• Europe 0.2
• Latin America Caribbean 1.7
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• North America 1.0
• Oceania 1.4
• Source UN World Population Data Sheet, 1996

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Very rapid growth

• Country Growth rate () Doubling time
  years
• Marshall Is 3.9
• Jordan 4.6
• Oman 4.2

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Slow growth rate

• Country Growth rate () Doubling time
  years
• Cook Is 1.1
• Samoa 1.0
• Tonga 1.0

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Most populous Countries
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Net Annual additions population in millions
1995-2000 (source US Census Bureau)
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World population growth
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World Population Growth

• Pre-modern growth before 1650
• Population growth very slow (about 0.05) due to
• Extreme weather conditions
• Fluctuation in food output
• Outbreak of diseases
• High mortality rates

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Modern population explosion 1650 to the present

• 1650 population 0.5 billion
• 2000 6 billion people
• Rapid acceleration in growth after 1650 was due
  mainly to the decline in death rate that
  accompanied the Industrial Revolution

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POPULATION GROWTH
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Reasons for unprecedented population growth

• Agricultural revolution- use of fertilizers,
  machinery, new techniques of crop rotation led to
  increase in food production
• Public health programs proper sanitation and
  safe drinking water
• Modern medicine, vaccinations and inoculations
• Improved transportation access to agricultural
  products from outside their area

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Other factors

• Lack of awareness of contraception or the ability
  to limit family size
• Lack of access to contraception unmet need for
  contraception
• Human reproduction is matter of religious and
  cultural importance
• Economic value of large families (farm labor,
  elder care and support)
• Status attached to high fertility

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Differential growth

• Not all population growth is exponential
• There are significant and different patterns of
  population growth in the MDCs and LDCs
• MDCs
• 1950-1960s growth rate fairly high and
  declining steadily since then
• Gradual decline in mortality and rapid decline in
  fertility
• Thus natural increase has declined
• It took a long time for both mortality and
  fertility to decline

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Differential growth

• LDCs
• Post WW2 growth rates twice as high as MDCs
• Growth rate peaked in 1960s and declining since
  then
• Mortality declining gradually
• Fertility did not decline as early as mortality
• Because fertility declined at different times
  there are variations in current growth rates in
  LDCs

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Figure 2.5 Population growth of more and less
developed regions 19962050
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IMPORTANT CONCEPTS

• Overpopulation involves the idea of scarcity,
  that is too large a population and inadequate
  means for subsistence
• Concept suggests tension between population size
  and resources
• Imprecise but widely used concept
• Overpopulation population
• space

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Important concepts

• Population
• Means for subsistence
• Means for subsistence includes
• Natural resources essential for human well-being
  and production (eg water, fresh air, a
  non-polluted environment, energy sources). It
  also includes other non-labour determinants of
  productive capacity eg investment capital,
  education, health services

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Problems of Size

• Carrying Capacity Its the maximal sustainable
  load that humankind can impose on the environment
  before it loses its capacity to support human
  activity
• Population Pressures Usually employed in
  relation to the living standards of the
  population

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Problems of Growth

• Population momentum
• Because growing populations have large
  proportions of children the growth rate will not
  fall to zero at once, even if replacement
  fertility level is achieved.

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Example of Momentum

• Think of the momentum that you experience when
  you are driving a car 60kph on a flat road
• Even after you take your foot off the
  accelerator, the car continues to coast forward
  for a period of time. Then after a few seconds ,
  speed begins to drop noticeably. After a period
  of time the car may slow down to 30 kph but the
  car will still be rolling forward. By the time
  the car stops altogether, it will have rolled
  well past the point where all acceleration
  ceased.

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Momentum

• Now imagine that instead of a car we are dealing
  with a large population and instead of an
  accelerator we have births
• Once a population reaches a certain speed of
  population growth, even if we take our foot off
  the accelerator by reducing fertility rates to
  replacement rates, the population will continue
  to coast forward or grow for many years because
  it includes many people of reproductive age.
  Populations continue to grow for another 50 years

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Recommended reading

• Zopf, P. 1984 The population explosion Myths
  and facts in P. Zopf, Population An
  introduction to social demography. Pp 3-21
• (this is in your reader)