Population Geography is the study of spatial variations in distribution, density, composition and growth of human numbers on earth.
It is important because it links all other aspects of geography together.
Demography is the study of population characteristics.
It is significant because
There are more people living today than any other time in history.
There's been a population explosion since World War 2.
There is an inverse relationship between population growth and resources i.e. there are too many people in places without enough resources to support them and too few people in areas with over abundant resources
Thomas Malthus, was a British Clergyman/economist.
He came up with the Malthusian Theory of Population Growth.
The salient points of his theory were
Food production increased at an arithmetic ratio (1, 2, 3...) while population increased at an exponential ratio (1, 2, 4, 8...).
Population growth would outstrip food supply, and mass starvation would follow.
Man is incapable of controlling his own numbers, so natural calamities such as floods and epidemics serve to control/reduce his numbers.
His theory was wrong in a number of ways:
He failed to foresee the agrarian revolution that would greatly increase food production.
Man has proven he is capable of controlling his numbers, such as in China withe the one-child per family policy.
The population has not grown as rapidly as he predicted.
Components of Population Change
Components of population change are births and deaths, immigrants and emigrants.
Fertility and Mortality
Fertility is the number of live births in a defined population. It is calculated using two main indices:
Crude Birth rate (CBR): the total number of live births / the total population x 100
Total Fertility Rate (TFR): the total number of live births / women of childbearing age(15-49) x 100
Mortality is the number of deaths in a defined population. It is calculated using two main indices:
Crude Death Rate (CDR): the total number of deaths / the total population x 100
Infant Mortality Rate (IMR): the number of infant eaths / the number of live births x 1000
Factors affecting fertility
Religion: most major religions favour family development so very religious populations have a high fertility.
Social customs and taboos, eg as regards contraception
Education. There is an inverse relationship between education level and the number of children .
Factors affecting mortality
Endogenetic processes. These refer to internal/bodily factors, such as disease.
Exogenetic processes. These refer to external factors such as the environment.
Other indices to gauge components of poulation change are
Life Expectancy. This is the the number of years a child can expect to live under current conditions. It is also the average length of life of a defined population.
The Natural Increase. It is calculated by the formula CBR - CDR / Total Population x 100
Migration is the movement of people
It is classified by such indices as
Reason for travel
Period of time of travel
Volume of migrants
Cosequences of migration include
Increased understanding between people of different cultures
Increased animosity between people of different cultures
Changes in numbers of people at the destination and origin
Creation of ghettoes in urban areas
Ravenstein's Laws of Migration
Ravenstein came up with his "laws" of migration in the 1880s based on studies carried out in the UK.
The laws are as follows
The greatest body of migrants travel short distances.
This produces currents directed towards great commercial centers.
Each current has a compensating counter-current in the opposite direction.
Both currents dispaly similiar characteristics
Long distance movements are directed towards great commercial centers.
People in urban areas migrate less than people in urban areas.
Males migrate more over long distances and females migrate more over short distances.
Additions to These Laws
Most migrants are between 20-34 years of age.
People mainly move for economic reasons.
Urban housing development is inadequate for the influx of migrants so ghettoes/shanties are formed.
Zipf's Inverse Distance Law
The volume of migrants decreases with distance from the origin.
Stouffer's Law of Intervening Distances
The number of migrants moving from one town (i) to another (j) is directly related to the opportunities available at j but inversely proportional to the number of intervening opportunities between i and j.
Any migration is as a result of push forces at the origin and pull forces at the destination. Examples of push forces are famine, war and poverty. Examples of pull forces are availability of food, peace and wealth.
This theory states that larger towns are more attractive to immigrants than smaller towns
Consequences of Migration
These can be subdivided into 3 categories:
Changes in the numbers and distribution of people within a region are changed.
Intermarriages are created, leading to a new group of people.
Migration brings different people together leading to conflicts.
Migration however also creates understanding between different groups of people.
Rural-Urban migration creates ghettoes in cities.
This depends on the "quality" of the migrants and the economic needs of the origin and destination. Quality refers to skills, age, educational attainment, health etc.
In overpopulated areas, emigration is beneficial because it reduces the pressure on the land.
In underpopulated areas, emigration may slow down development.
The sex structure refers to the proportions of the 2 sexes in a defined population.
It is expressed as the number of males to every 100 females.
Male births usually exceed female births, but males die off more quickly in infancy, so by the time children are 1 yr old, there are more females than males.
The sex structure may be affected by the following
Where women are considered subordinate beings, they suffer a higher mortality rate and a lower life expectancy.
Migration. There is usually a dominance of males in populations dominated by immigrants.
In difficult environments, there is usually an imbalance in favor of males.
Select populations such as military towns may have an imbalance for either of the sexes.
Urban areas in developing regions have more males.
There are 3 basic age structures:
Progressive (Brazilian) Type
Stationery (American) Type
Regressive (European) Type
It has a wide base that quickly narrows upwards to a point.
It indicates a large birth rate, but poor conditions mean people rapidly die off, hence the triangular shape of the structure. The population is increasing.
The shape of this structure is more "square." All age roups are well represented.
It indicates that the birth rate is moderate, and few people die off as they get older. The population is stagnant.
The structure has a fairly wide top with a bulging middle and narrow base.
The birth rate is low, hence the low base, and there are more adults than children. The population is decreasing.
The Dependency Ratio
This is the ratio between the non-working population (children and aged) and the workers (adults).
It is lowest in regressive populations and highest in progressive populations.
It is calculated using the formula (children + aged)/Adults) * 100
In developed countries, the DRs range from 50-70. In most developing countries the DRs are over 100
The Old Age Index
This is the proportion of aged to adults.
It is calculated using the formula: (aged)/(adults) * 100
Theories of Population Change
These are theories to explain the patterns of population growth in different countries of the world.
Biological Theory: This theory states that man is like any other living thing. He is incapable of controlling his growth in numbers.
Cultural Theory: This theorstates that man is rational and uses his intellect yo control his growth in numbers, eg the one-child policy in China
Economic Theory: Based on Marxist-Leninist theories, it supposes that growth in population is as a result of a demand for labor.