why does population growth vary among regions? chapter 2 key issue 3
TRANSCRIPT
Why Does Population Growth Vary Among Regions?
Chapter 2 Key Issue 3
Demographic Transition Model
Explaining Spatial Patternsof World Population GrowthMany graphics in this powerpoint are from Michael Kuby et al.,
Human Geography in Action (instructor package) or online materials posted by Keith Montgomery, Dept of Geology and Geography, Univ
of Wisconsin - Marathon County (http://www.uwmc.uwc.edu/geography/Demotrans/demtran.htm)
The Demographic Transition
• Process of Change in society’s population from high CBR, CDR, and low NIR to a condition of low CBR, CDR, and NIR
Demographic Transition Model
DTM only predicts changes in birth/death rates over time
Observed changes in NIR correlate to changes in economic development
Thus, DTM implies:The greater the wealth,the lower the NIR... but use caution describing this relationship
Stages in Classic 4-Stage Demographic Transition Model (DTM)
(Some books show a 3-stage model; others mention a new 5th stage)
Stage 1: “Pre-Industrial”
High birth rates and high death rates (both about 40)
Population growth very slow
Agrarian society
High rates of communicable diseases
Pop. increases in good growing years;declines in bad years (famine, diseases)
No country or world region still in Stage One
Stage 2: “Early Industrial”
High birth rates (over 30) but death rates decline (to about 20)
RNIs increase sharply (pop. explosion); growth rate increases thruout Stage Two
Growth not from increase in births, but from decline in deaths
MDCs = starts early 1800sLDCs = starts after 1950s
TRANSITION TO STAGE TWO IN CLASSIC DTMKnown as the Epidemiologic Transition
Agricultural technology
Improvements in food supply: higher yields as agricultural practices
improved in “Second Agricultural Revolution” (18th century)
In Europe, food quality improved as new foods introduced from Americas
Medical technology
Better medical understanding (causes of diseases; how they spread)
Public sanitation technologies
Improved water supply (safe drinking water)
Better sewage treatment, food handling, and general personal hygiene
Improvements in public health especially reduced childhood mortality
Declining Infant Mortality Rates
When IMR declines, fertility rates drop soon after
Stage 3: “Later Industrial”
Birth rates decline sharply (to about 15)
Death rates decline a bit more (to about 10 or less)
Note growth still occurs, but at a reduced and declining rate
MDCs = starts in late 1800sLDCs = starts after 1980s*
* Or hasn’t started yet
Measles Mortality, US, since 1900
TB Mortality, US, since 1900
Stage Three:
Further improvements in medicine lower death rates more; raise life expectancies
TRANSITION TO STAGE THREE IN CLASSIC DTMKnown as the Fertility Transition
Societies become more urban, less rural
Declining childhood death in rural areas (fewer kids needed)
Increasing urbanization changes traditional values about having children
City living raises cost of having dependents
Women more influential in childbearing decisions
Increasing female literacy changes value placed on motherhoodas sole measure of women’s status
Women enter work force: life extends beyond family, changes attitude
toward childbearing
Improved contraceptive technology, availability of birth control
But contraceptives not widely avail in 19th century; contributed little to
fertility decline in Europe … Fertility decline relates more to change in
values than to availability of any specific technology
Population Classified as Urban
Rapidly increasing urbanization in world LDCs today
Strong inverse relationship between female literacy and fertility rates, observed globally
Increasing availability and use of modern
contraception in most LDCs since
1970s
Stage 4: “Post-Industrial”
Birth rates and death rates both low (about 10)
Population growth very low or zero
MDCs = starts after 1970sLDCs = hasn’t started yet
Stage 5 (?): Hypothesized (not in Classic DTM)
Much of Europe now or soon in population declineas birth rates drop far below replacement level
Key Population Indicators for Selected Countries
Differences in DTM experience: MDCs & LDCs● Faster decline in death rates — Tech improvements diffused from MDCs & applied rapidly in LDCs post-WW2
● Longer lag between decline in deaths and decline in births — Stage 3 slower start in LDCs where econ growth is delayed
● Higher max rates of growth in LDCs — Over 3.5% peak RNI in Mauritius and Mexico; only 1.3% peak in Sweden
Percentage of Population Under Age 15
Age structures today in LDCs are much younger than MDCs experienced – leading to prolonged “Demographic Momentum” – expected growth of pop. long after fertility declines
The Demographic Transition
Fig. 2-13: The demographic transition consists of four stages, which move from high birth and death rates, to declines first in death rates then in birth rates, and finally to a stage of low birth and death rates. Population growth is most rapid in the second stage.
Population Pyramid of the U.S.
Population Pyramids in U.S. cities
Fig. Population pyramids can vary greatly with different fertility rates (Laredo vs. Honolulu), or among military bases (Unalaska), college towns (Lawrence), and retirement communities (Naples).
Rapid Growth
in Cape Verde
Cape Verde, which entered stage 2 of the demographic transition in about 1950, is experiencing rapid population growth. Its population history reflects the impacts of famines and out-migration.
Moderate Growth in
Chile
Chile entered stage 2 of the demographic transition in the 1930s, and it entered stage 3 in the 1960s.
Low Growth in Denmark
Denmark has been in stage 4 of the demographic transition since the 1970s, with little population growth since then. Its population pyramid shows increasing numbers of elderly and few children.
• Critics – Based on England– Billions and much faster then ever before– Graying Population – Medical Revolution- 1900’s
• Demographic Momentum (hidden momentum)
Summary of DTM for LDCs
Industrializing LDCs with some economic development follow DTM more closely; now in Stage Three. Most like MDCs in places where female literacy has increased the most.
Lowest-income countries have high birth rates and deaths are leveling off at higher rates than DTM predicts (Stage Two).
In some LDCs, death rates starting to increase (epidemics, worsening poverty)
Dependency Ratio
• # of people too old (65 years & up) or too young (0-14 years) to work compared to the # of productive workers
Fig. 2-12: The crude death rate (CDR) is the total number of deaths in a country per 1000 population per year. Because wealthy countries are in a late stage of the Demographic Transition, they often have a higher CDR than poorer countries.
Percent of Population Under
Age 15
Sex Ratio
• # of males per 100 females in the population
POPULATION STRUCTUREThe population pyramid displays the age and sex structure of a country or given area
Usually, but not always,in % to make for easiercomparisonsbetween countries
FEMALESTo the rightMALES
To the left
Population inFive YearAge bands
OLD DEPENDANTS
ECONOMICALLYACTIVE
YOUNG DEPENDANTS
What Population Pyramids Show Us
KEY
slope of pyramid indicate the death rate
width of the base is related to birth rate/fertility rate
proportions of men and women can suggest male or female migrations
height of graph can indicate life expectancy (ignore the very thin end of the wedge as occurs on graph B as these people are a definite minority)
"kinks" indicate dramatic reductions in birth rate or increases in death rate in the past
area of graph indicates total population - compare areas of differentpopulation age groups or different sex on one graph
The overall shape of the population pyramid can indicate whether it is an Economically More Developed Country or Economically Less Developed Country
Economically More Developed Country
Economically LessDeveloped Country
Population Pyramids related to the Demographic Transition Model
Stage 1 Stage 2 Stage 3 Stage 4
Both birth rates andDeath rates areHigh, so populationgrowth rates are slow but populationIs usually restoredDue to high birth Rate. Short lifeExpectancy
EXAMPLES: none today - Afghanistan, Ivory Coast (30 years ago)There are no Stage 1 countries today
Population startsto grow at anexponential rate due to fall in Crude Death Rate. More living In middle age.Life expectancy risesInfant mortality rate falls.
EXAMPLES: DR Congo, Yemen, Afghanistan (today)
Population continuesto grow but at slowerrate. Low C Death Rate.Dramatically decliningCrude Birth Rate.
EXAMPLES: India, Brazil (late 3) – Most of world is in 3
IMPLICATIONS IMPLICATIONS IMPLICATIONS IMPLICATIONS
Low Crude Birth Rate and Crude Death RateHigher dependency ratioand longer life expectancyCrude Death Rate does Rise slightly because ofThe ageing population
EXAMPLES: China, United States, Canada, Australia
There is some merit in including or considering a Stage 5 today with a declining population- Europe - Japan
Practice with real pyramids-What Stage of DTM?
3
2
4
5
Practice with real pyramids-What Stage of DTM is US? Challenging – why?
2011 Data• TFR 2.1• BR 14• DR 8• Natural Increase: .6%• Growth Rate: .9%
• Why is Growth Rate higher?
• How does this impact pyramid?
• Pyramid looks like a late 3 country.
• But does US fit description profile of Stage 4 better?