Download Understanding Demography

Bell Work
 Demographers study POPULATION
 Make a prediction: What certain attributes
“characteristics” of a society might demographers focus
on?
Understanding
Demography
Objective: Explain the key terms of demography. Analyze
population pyramids.
The Study of Population
 Every country goes through a change in its population
structure as it develops – this is called the demographic
transition
 Important terms to understand:
 More Developed Country (MDC) or Developed
 Less Developed Country (LDC) or Developing
What do demographers look at in a
country?
 Crude Birth Rate (CBR) - #
of people born every year
per 1000 people
 What factors do you think
affect CBR?
 Wealth, medical advances,
opportunities for women, low
infant/child mortality rates,
availability of contraceptives
 Crude Death Rate (CDR) - #
of deaths every year per
1000 people
 What factors do you think
affect CDR?
 Better/more stable access to
food, access to medicine,
composition of population
(lots of old people?),
epidemics, famine, sanitation
facilities
CBR and CDR determine the…
 Natural Increase Rate (NIR) – percentage by which a
population grows in a year
 The difference between CBR and CDR
 CBR minus CDR
 Sometimes called natural change
 NIR affects the Doubling Time
 # of years it takes to double the present population at
current growth rates
Doubling Time Riddles
A father complained that his son’s allowance of $5 per week was
too much. The son replied, “OK Dad. How about this? You give
me a penny for the first day of the month, 2 cents for the second,
4 cents of the next, 8 cents of the next and so on for every day
of the month.” His father readily consented
 Who was more clever?
 What would the son’s allowance be on day 31?
 What would his allowance for the month be?
 Do you know how long it will currently take for the world’s
population to double?
Another riddle
Doubling time is the time it takes a population to double at a
constant rate of growth. Bacteria, for instance, multiply by
division. One bacterium becomes two. Then two divide into
four; the four divide into eight, and so on. For a certain strain
of bacteria, the time for this division process is one minute.
 If you put one of these bacterium in a bottle at 11pm, the
entire bottle will be full by midnight. When would the bottle
be half full?
 How do you know?
 Suppose you could be a bacterium in this bottle. At what
time would you first realize that you were running our of
space?
Demographers also study…
 Total Fertility Rate (TFR) – the average # of children a
woman will have throughout her childbearing years
 When a country has a TFR at or less than 2.1, the
population is not growing – only maintaining itself –
because couples are only having enough children to
replace themselves
 The magic number 2.1 is called the Replacement Rate
 2.1 TFR/Replacement Rate results in…
 Zero Population Growth (ZPG) – same # are born and
die in a year, CBR=CDR
Population Pyramids
 A visual representation of age and gender cohorts (groups)
within a country
 MDC’s and LDC’s will have different looking population
pyramids because they have different population structures
 Shape of the pyramid is determined by the CBR in each
country
 Pyramid shows the percentage of the total population in 510 year age groups
 Males shown on the left, females on the right
 Now, we’re going to practice drawing population pyramids!!