In 1800, global population was 1 billion. By 1960, it had reached 3 billion and it doubled to 6 billion in 1999. Now, we are at 7 billion this year (2011).
It is predicted we will reach 9 billion by 2050. Estrimates are that the world population will peak at 9.22 billion in 2075. Projections to 2300 expect world population to be 8.97 billion - these estimated are obviously, uncertain as they do not take into account disease, rising sea levels etc.
The world's most populous country is China with a current population of over 1.3 billion. Second is India with 1.1 billion but will likely overtake China by 2030. You can see that these two countries alone comprise about 1/3 of the world's population. The US is third with 296 million and is still continuing to grow - which is rare amoung developing countries.
EXPLOSION OR LACK OF BIRTHS?
Birth rates remain higher than replacement level (2.1 for stable population) in many LEDCs. Most women are having fewer children than their mothers, however, the sheer amount of young people in these countries - many Asia and Africa have over over 40% of the population under 15 - means we will continue to grow for many years. This is called population momentum.
In MEDCs, particularly in Europe, we have the opposite problem. Women are having fewer children than replacement level and populations are ageing. For women in MEDCs, the average life expectancy is 80. One of the solutions to the European population problem is to increase immigration, but this has been politically unpopular.
Random fact - In Russia, women are being paid the equivalent of $11,000 to have a second child.
What do you understand by the term replacement level fertility?
This is when the fertility rate in 2.1. There are just enough babies being born to replace their parents without the population expanding rapidly. The .1 mean there are few extra children as some may not live / be able to have children of their own.
COMPONENT OF POPULATION CHANGE
Population change for any given country region is the outcome of the balance between two components; natural change and net migration.
Natural Change = Number of birthday - number of deaths.
When births exceed deaths then the change is natural increase; when deaths exceed births, the change is a natural decrease.
Net Migration = Number of immigrants - number of emigrants
The balance between these two equations is expressed in terms of the following simple equation
Population change = Natural Change + Net Migration
Between 1991 and 1997, the population of the UK grew from 57.8 million to 59.0 million, an average increase of 200,000 people a year. We can derive the relative importance of the two components of change from this data:
Mean annual number of births = 753,000
Mean annual number of deaths = 640,000
Mean annual net migration +87,000
Population change:(753,000 - 640,000) + (87,000) = 113,000 + 87,000 = 200,000.
Even within such a short time-sale, there may be considerable variation in contribution from the components.
SEE FOLLOWING NOTES FOR COMPONENTS
This is the measured capacity of a population to generate births. It is measured in 2 ways; birth rate and fertility rate.
- Crude birth rate: The number of births per 1000 people per year
- Total fertility rate: The average number of children born to a woman during her child bearing years (15 - 49) in an area.
This is the measured capacity of deaths in a population. It is measured in 3 ways; Crude Death Rate, Infant Mortality and Life Expectancy
- Crude Death Rate: Number of deaths per 1000 people per year
- Infant Mortality: Number of deaths of children under the age of 1 per 1000 per year
- Life Expectancy: Average number of years a person can expect to live.
The movement of people into or out of a specific area. Migration adds of subtracts from an area's population depending on whether more people move in or out.
GLOBAL CHANGES OVER TIME
For most of human history, the world's population never exceeded 10 million people.
The death rate was about as high as the birth rate, and the rate of population growth was scarcely above zero. Significant population growth began about 8000 B.C, when humans began to farm and raise animals.
By 1650, world population expanded about 50 times - from 10 million to 500 million. Then world population shot up another 500 million people in just 150 years, reaching it's first billion around 1800.
It achieved its second billion by 1927, 123 years later. A third billion by 1960, only 30 years later. Fifteen years later, it reached 4 billion.
It then took 35 years to increase to seven billion - where we are today.
DENSITY AND DISTRIBUTION
Population density is the number of people per unit area.
The density of population is obtained by dividing the total population of a country (or region) by the total area of that country (or region).
The density of population for a country can be misleading as it not show how variations between densely populated regions and those areas that are almost unpopulated. The typical form of displaying population density is through a chloropleth map.
Population distribution describes the way that people are located within an area.
When plotted on a map, this can reveal these areas that have a high population and those where few people live, which maps of population density fail to show. One of the ways of plotting this information is through a dot map.
Migrants move from less-affluent, more developed nations to the more affluent ones - eg: Portugal to France.
They also move from the poorer, less developed nations to relatively prosperous ones - eg: Colombia to Venezuela
The most obvious reason for migration is from a less developed country, to a more developed country - eg: Mexico to the USA.