1. FACTORS OF POPULATION CHANGE
There are 3 major factors that contribute to population change
(both natural increase and decrease)
FERTILITY
MORTALITY
MIGRATION -
(NOT ‘natural’ population change BUT can indirectly influence natural increase or decrease and of course population size/numbers through immigration (in) and emigration (out)

2. FERTILITY – the reproductive level of a population
Crude Birth Rate (CBR) – most common measure of fertility. It gives an overall picture of the number of births per 1000 population in a year
CBR = total number of births x 1000
Total population
Total Fertility Rate (TFR) – Average number of children a woman will give birth to in her lifetime. A TFR of over 2 means the popn is expanding; TFR below 2 the popn is contracting (getting smaller)
This varies hugely across the globe & is linked to levels of development Eg. UK 1.7 Singapore 1.4 children, Sierra Leone 6.5
Replacement Level fertility (RLF) – level at which each generation of women has only enough daughters to replace themselves in the population.
Normal figure given for replacement level children
Since 1995 there has been a steady decline in RLF across the world
Actual & Desired Fertility rates –
Actual (what happens) desired (how many a woman would ideally want) eg.
Italy: Desired 2.1 Actual 1.65 Austria Desired 2.0 Actual 1.69

3. CDR = total number of deaths x 1000
MORTALITY
Mortality is the ratio of deaths to the population of a given area. Mortality is often measured using such indices as crude death rates, infant mortality rates or life expectancy
Crude death rate (CDR) gives a overall picture of mortality & is expressed in number of deaths per 1000 population per year
CDR = total number of deaths x 1000
Total population
According to population census data, 2003, Singapore had a CDR of 11 per 1000, Sierra Leone 25 per 1000, so for every 1000 people 11 deaths were recorded in Singapore, 25 SL!
CDR can be misleading however, as it does not take into account life expectancy. Eg France & Togo had CDR of 13/1000 in 1994, but people can expect to live 22 years longer in France than Togo
High DR may not indicate unfavourable living conditions, eg. the higher death in Devon & Florida reflects the fact that many elderly people wish to live in such areas (retirement attractions). As such, DR will rise and BR will fall for these sorts of areas!

4. Many African nations have very high rates of IMR
MORTALITY
Infant Mortality Rate (IMR) – Number of children who die before their first birthday, per 1000 live births per year.
Since children are much more susceptible to sickness and disease than adults, the no. of infant deaths is a very reliable indicator of the state of the health in a country.
Many African nations have very high rates of IMR
Life Expectancy - Average number of years a person can expect to live. High mortality in the early age groups lowers the average life expectancy. Again, a good indicator of development
Maternal Mortality Rate (MMR)– Number of women who die as a result of complications during pregnancy & childbirth. Expressed per 1000 live births in a year. MMR far higher in LEDCs, esp Africa where women are 200 times more likely to suffer a pregnancy related death than women in Western Europe
Why? Poor access to health facilities, higher fertility rates (less chance to recover) & poorer diet (less resistance to disease & infection)

5. POPULATION GROWTH RATES
The difference between crude birth rates and crude death rates is the rate at which the population either increases / decreases. This is natural population change and does not take into account migration!
With a CBR of 41 per 1000 (4.1%) & a CDR of 13 per 1000 (1.3%) as Nigeria had in 2002
The annual popn growth rate is calculated as 4.1% - 1.3% = annual growth rate of 2.8%
Rates of population increase can be deceptive in that % seem unimpressive eg.a growth rate of 1.3% seems very small.
However, World’s population of 6 billion growth rate of 1.3% = doubling time of 54 years if current rates are maintained – so by 2058 the global population may stand at 12 billion!
Simple method to calculate doubling time – divide 70 by the natural increase, this a country with a popn increase of 1% double in 70 yrs, 2% 35 yrs etc

6. MIGRATION
Although migration (both immigration & emigration) can influence population size it does not count for natural increase or decrease.
However, migration can have an indirect influence on natural population increase or decline within a specific country over time.
Case study: Hispanics in the USA
Case Study: Immigration & the impacts on the UK (population & services)
& handout
Why are immigrants to the USA & UK having such an impact on the overall population ?
What issues (both positive & negative) does this natural increase in the population (through migration) bring?