SUMMARIES UNIT 11 : WORLD POPULATION (2ºESO)

1. DISTRIBUTION OF WORLD POPULATION

WHAT IS WORLD POPULATION?

World population is the total number of people living on Earth. His figure reached 7,000 million in 2012. Population has grown continuously for many centuries, but not always at the same rate:

• World population increased slowly before the 18 th century. Great epidemics, like the Black Death in the 14 th century, interrupted growth.
• During the 18 th and 19 th centuries, population grew in Europe and North America. As a result of improved agricultural techniques, more food was available to people. Advances in medicine and sanitation improved public health so people lived longer.
• The 20 th century was the period of greatest population growth in all human history in almost every part of the world. Between 1900 and 2000, the Earth’s population increased from 1,600 million people to more than 6,000 million. Today, world population is increasing, but not quite as quickly as before. Most population groth takes place in developing countries.

POPULATION DENSITY

We measure population density to see how population is distributed. This is the total population of a territory divided by its surface area. Results are expressed in the number of inhabitants per square kilometre (or km2) :

Population density=  Total population/Area (in km2 )

Average population density across the orld’s entire land surface (excluding Antarctica) is about 50 inhabitants per km2 .

But there are huge differences between one region and another. Some areas have high population density, while others have extremely low population density.

WHY IS POPULATION DISTRIBUTION UNEVEN?

The uneven distibution of he world ‘s population is due to physical and human factors:

• Physical factors. Some types of ntural environment usually have high population density. Favourable conditions include abundant water, a températe climate, low fertile land, and mineral resources. On the other hand, regions with little water or extreme temperaturas are less densely populated.
• Human factors. Historically, opulation settlement has developed in certain parts of the world. Regions like the great river valleys of the Nile and the Ganges, or the east coast of China have been settled for thousands of years. Today, population density usually reflects economic activity. A region with considerable industrial, mining or agricultural production is likely to be densely populated.
• In recent centuries, cities have attracted large populations by offering job opportunities and becoming the centres of transport networks.

2. POPULATON GROWTH

WHAT IS DEMOGRAPHY?

Demography is the scientific study of human population. It examines population trends in the past as well as its present –day charactristics. Demographers measure population growth by using a number of rates, like the birth rate, fertility rate and mortality rate. (A rate is the ratio between two measurements). By comparing all these indicators, we can analyse populaion growth in different countries or regions.

THE BIRTH RATE AND FERTILITY RATE

The birth rate measures the number of births in an area over a year. It shows anual births per 1,000 people.

The birth rate is closely related to the fertility rate. This is the average number  of babies born to women over the entire period when they can have children, between the ages of 15 and 45.

Many different factors affect the fertility rate. It is influenced by cultural and economic factors such as whether women work the age when they begin to have children and the availability of contraceptives.

The birth rate and the fertility rate have vried greatly in different places and periods. Before the 19 th centry , both rates were very high everywhere. But in the 19 th and 20 th centuries, the number of births began to fall rapidly in more developed countries. At the same time, the birth rate and fertility rate stayed at very high levels in poorer countries and remain that way today.

THE MORTALITY RATE

The mortality rate measures the number of deaths in an area over a year. It shows anual deaths per 1,000 people.

Mortality rates have changed greatly over the centuries. Before the 19 th century, they were generally high because people had por health and nutrition. This made them vulnerable to epidemics.

But in the 19 th and 20 th centuries, living conditions improved in developed countries and the situation changed. In recent decades, the mortality rate has fallen in many developing countries thaks to health programmes and improved sanitation. But infant mortality rate is still very high in regions like Africa.

At the same time, in recent years, the proportion of older people in developed countries has increased considerably. Older peole are much more lokely than younger people to die each year. Consequently, the difference between the mortality rate in richer and poorer countries has declined.

NATURAL INCREASE AND LIFE EXPECTANCY

Natural increase is the difference between the number of births and deaths in a populaion. It is positive when the birth rate is higher than the death rate, but it is negative when there are more deaths than births.

Today, natural increase is low or negative in many developed countries. Their population only grows slowly unless they receive a good deal of inmigration. On the other hand, it is high in most parts of Asia, Africa and Latin America.

It is posible to give absolute figures for natural increase, but we usually measure the rate of natural increase. This figure is calculated by subtracting the mortality rate from the birth rate.

Another key indicator in demography is life expectancy at birth. This is the average life span of people in a particular society. Life expectancy has risen greatly, but still varies very much from one country to another. In developed countries, the figure is about 77 years, but it is only 45 in the poorest counries.

3. DEMOGRAPHIC STRUCTURE

WHAT IS DEMOGRAPHIC STRUCTURE?

The demographic structure of a population is its distribution in different groups according to age and sex.

This structure is very different from one country to another. But it may also vary in different regions in the same country. It reflects the birth rate, mortality rate and migration.

A populaion is divided into hree main age groups:children (0-14 years old), the population of working age (15- 64 years old), and older people (over 65 years old).

The demograhic structure of an area reflects its level od development. Some regions have Young populations, while others have ageing populations.

THE YOUNG POPULATION OF DEVELOPING COUNTRIES

Developing countries generally have Young populaions as a result of their rates of natural increase.

In many of these countries only about 8% of the population is aged over 65, while more than 30% of the population is in the youngest age group (0-14 years old).

Rapid population growth creates major problems for these societies. For example, they may not have enough economic resources to build new schools or guarantee basic services.

For this reason, some countries adopt anti-natalist policies. To reduce the birth rate, they make contraceptives widely available and encourage family plannin. In a few cases, such as China , there have been penalties for families with more than one child.

THE AGEING POPULATION OF DEVELOPED COUNTRIES

The population of most developed countries is ageing. This is the resukt of:

• Increased life expectancy. Medical advances and improvements in nutrition and living standars mean that people live longer. Consequently the proportion of people aged 65 or older increases.
• Declining birth rate. Many women have careers in develop countries and may wait before they have children. families are used to a fairly high standard of living, so they prefer not to raise several children.

As a result, the population of these countries is gradually getting older. Today, people aged 65 or older make up about 20% of the total population while Young people, aged 15 or less, only reresent  17%. Demographers forecast hat the proportion of older people in the population will continue to increase.

An ageing population will be a major problema for developed countries in the future. Societies will need to find economic resources top ay for pensions and medical assistance. In some countries, pro-natalist measures have been taken, such as financial measures in favor of families with children.

4. MIGRATION

WHY DOES MIGRATION TAKE PLACE?

• Migration is the long-term movement of people from one place to another. The people who move are called called migrants.
• Emigration is the migration of people leaving heir own country or region to live in a different area. The people who leave are called emigrants.
• Inmigration is the migration of people arriving at their new place of residence. These people are called inmigrants.

Net migraion rate is the dfference between the number of emigrants and inmigrants in a region over a eriod of time. This is positive when more eople arrive in a region than leave it. A prosperous country usually attracts inmigrants. But a region with economic problems may have negative net migration. In this case, more people leave as emigrants than arrive as inmigrants.

Migrations take place for many reasons. Some eople mígrate as a result of natural disasters or to escape from wars and political persecution. But most people today do it for economic reasons.

INTERNAL MIGRATION

Internal migration is the movement of a population from one region to another inside the same country. Rural exodus (or flight) is one of the most imortant types of internal migration. It occurs when people leave the countryside to go and live in cities:

• In developed countries, there was a significant rural exodus throughout the 19 th and 20 th centuries. In the countryside, agricultura became mechanised and required fewer workers. At the same time, cities grew in size and offered greater economic opportunities.
• Rural exodus has been more recen process in developing countries. Many Asian, African and Latin American cities expanded enormously in the second half of the 20 th century. But there have not always been enough jobs, housing and transport services for so many new urban residents. As a consequence, unemployment, poverty and unhealthy living conditions have all become huge problems.

INTERNATIONAL MIGRATION

International migration is the movement of people from one country to another. There have been many different types of human migration throughout history:

• Many people went from Europe to America in the 19 th and early 20th centuries. These European emigrants left in search of better economic opportunities.
• The Slave Trade was a forced migraion. Africans were transported to America to work on agricultural plantations.
• From the 19 th century onwards, large numbers of Chinese citizens went t olive in other Asian countries and in American cities.

Today, here are may different types of migration. Emigrants leave the less developed countries of Asia, Africa and Latin America to find work and improve their living conditions. They often help family members who go on living in their home country. But qualified Young people i developed countries also leave home when they cannot find a job in their own country.

5. THE IMPACT OF MIGRATION ON DEMOGRAPHIC STRUCTURE

WHAT ARE THE CONSEQUENCESOF MIGRATION?

• Migration affects the demographic structure of the population. It produces changes in both the native countries of migrants and the ones in which the settle.
• The interaction of populations with different cultures has great social impacto n the countries that receive migrants.

EFFECTS ON THE HOME COUNTRIES OF MIGRANTS

Emigration has both beneficial and harmful consequences for the native countries of migrants.

• It creates a source of income. Emigrants usually transfer some of their savings back to their families in their home country.
• It may prevent unemployment reaching extremely high levels. If fewer people of working age stay in a country, there is less competition for the remaining jobs.

On the other hand, emigration has many harmful consequences:

• Countries lose highly qualified and well-trained workers when they decide to look for better profesional opportunities abroad. If they are successful, their friends sometimes decide to follow them.
• Younger people are much more likely to emígrate than older eople and age strucure becomes unbalanced when this happens.
• More men than women emígrate from many regions, so gender structure is also affected.
• Family life is badly disrupted when family mebers are searated from each other.

CONSEQUENCES FOR DESTINATION COUNTRIES OF MIGRANTS

Inmigration also has a great influence on the destination countries:

• Age. Populations grow and get younger. The arrival of Young people leads to an increase in the birth rate. This is especially beneficial for regions lie Europe that have ageing populations.
• Wealth. Inmigrants contribute to the economy by working and paying taxes.

On the other hand, inmigration is not always an easy process:

• Inmigrants may have problems of adaptation. Racism is a widespread problema.
• Mafias sometimes exploit ilegal inmigrants, by taking them across frontiers without oficial papers. These immigrants then find themselves in a very difficult situation.

WHAT IS A POPULATION PYRAMID?

A population pyramid breaks down a population according to age and sex. All the people who live in a region are divided into five-year age groups, which are represente don a bar graph. Younger people are shown at the bottom of the pyramid and older people at the top.

This type of graph is a very useful way of showing the demographic characeristics of a region, how it has developed in the past and how it will change in the future.

1. Collet the data.
2. Draw the pyramid.

Draw a vertical axis and a horizontal axis on graph paer.

The left side of the horizontal axis is for men and the right side is for women. He vertical axis gives age groups in five-year periods. The youngest age group is at the bottom and the oldest at the top. Each group is represented by a single bar.

3. Analyse the pyramid. We need to look at its shape.

1. Pyramids with a triangular shape have a high birth rate and a high mortality rate. There is a very low proportion of older people. This shape is characteristic of societies that have not yet reached a high level of development.
2. An inverted pyramid indicates a declining population. It may be found in developed countries with a low fertility rate and high life expectancy.