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Population. Vocabulary Effects of high population levels and growth Current situation Projections What drives population growth? Momentum and Fertility What causes changes in fertility Demographic Transformation or Trap? How accurate are projections? Strategies for changing fertility.
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Population Vocabulary Effects of high population levels and growth Current situation Projections What drives population growth? Momentum and Fertility What causes changes in fertility Demographic Transformation or Trap? How accurate are projections? Strategies for changing fertility
Vocabulary (2) • Dependency Ratio = Dependent PopulationWorking Age Population • Momentum
What Drives Population Growth Patterns? • Momentum • Fertility • Shocks
Population momentum in Mexico 1980-1998: Large increase in women in childbearing years, this, even if fertility stays constant, population will increase
What Causes Changes? • Hypothesis: Social and economic development lead to a demographic transformation • Industrialization, urbanization, education and general modernization lead to a decline in death rates and then a decline in birth rates • This seems to have been the case for presently rich countries. Is it true for countries that are now developing?
Will there be a demographic transformation in Africa or will rapidly growing population overwhelm development efforts?
Projections and Evidence about Demographic Transformation in LDCs
Only a Small Decline of Sub-Saharan African Fertility Rates 1970s to 1980s
Declines in Latin American and Caribbean Fertility Rates 1970s to 1980s
How accurate are population projections? Source for this discussion is Cohen, Joel. 1995.How Many People Can the Earth Support? New York: W.W. Norton & Company
Cohort component method assumes that females of child bearing ages in, e.g., 1995 will have same fertility pattern as those in 1990.
Projections of UK’s 2001 population made over 17 years: 25% upward adjustment 1960-1965; 37% downward adjustment 1965-1977UK is small and homogeneous thus ideal for projections.Actual 2001 population was 58.8 million
Do high and low projections provide an adequately wide band?
UN’s high and low projections of 1980 world population overlap, i.e., the band was too narrow - it indicated more confidence than warranted