Mortality transition (lower)
- Improvements in the standard of living esp. quantity and quality of food.
- Improvements in public health measures e.g. draining of mosquito-infected swamps and securing clean water.
- Role of medical treatments in curing diseases.
Fertility transition (lower)
- Improved contraception
- Cultural shift in favour of fertility control.
- Although total fertility is not that much higher than desired fertility
- Economic growth --> lower desired fertility because of 1. lower mortality 2. income & substitution effects (where price of children is higher) esp. opp cost of women not working 3. Resource flows between parents and children 4. Quality-quantity trade-offs.
Replacement rate of fertility is roughly 2.1 children per women would require both an increase in fertility in developed countries and a decrease in fertility in developing countries.
- Predict a generally declining world population growth rate stabilising at around 11 billion by about 2150.
- In developing world mortality rate has fallen faster than fertility thus populations are still growing.
- Low Total Fertility Rate (TFR) may be due to a tempo effect where women are delaying the age at which they have children however this can only explain 0.25 to 0.4 of the reduction.
- Demographic momentum is where the number of fertile women boosts population growth even if the rate of fertility stays the same.
- Demographic structure particularly the percentage of the population of working age is significant for GDP/capita. E.g. In US fraction of working age population is forecast to fall from 0.6 to 0.54 which owould in a 20 year period have a -0.5% effect on GDP/capita.
- Composition effect means that world GDP is declining as a larger proportion of the worlds population is from poor countries.