HOW CAN WE KNOW IF A POPULATION IS GROWING OR DECREASING?

We can measure the birth rate and the death rate

If the birth rate is bigger, population will increase

If the death rate is bigger, population will decrease

As a result, we can measure the NATURAL INCREASE of the population

Where are the countries with the

highest natural population increase

or growth?

Where are the countries with a negative natural

population growth?

THE BIRTH RATE:

It is the average number of live births in a year for every 1000 people in the total population

THE DEATH RATE:

It is the average number of deaths in a year for every 1000 people in the total population

The NATURAL INCREASE (decrease) is the difference between the birth rate and the death rate

FERTILITY RATE

The fertility rate is an estimate of the average

number of children a woman will have during

her lifetime

It is measured using the Total Fertility Rate:

TFR= Number of births / number of women who are between 15 and 49

There are other important factors to know and predict the growth of the population

To ensure population replacement levels, the fertility rate must be at least 2.1 children per

woman

INFANT DEATH RATE

Infant Death Rate indicates the number of children who die before their first

year per 1000 babies born during one year

The formula is:Number of deaths of babies under one year

divided byNumber of life births in that year

LIFE EXPECTANCY

It is the average number of years that a person can live in a country

In which countries would you expect to find a high infant death rate?

Why do we talk about “natural” population increase?

What other factors could affect population size?

Throughout the history the population has increased

- Until the 19th century, world population grew slowly.- In 1750, there were only 800 million people on the Earth- Improvements in agriculture and medicine in developed countries reduced the death rate and the population increased rapidly- By the end of the 19th century, the world’s population reached 1.7 billion of people- Population growth very fast during the second half of the 20th century:

From 3 billion in 1960 to six billion in 1999. - Today the population has reached seven billion of people

Which are the main problems of this fast

growth?

Is the growth the same in all the

countries?

DEFINITION OF THE DEMOGRAPHIC TRANSITION MODEL

The demographic transition model seeks to explain the transformation of

countries from having high birth and death rates to low birth and death rates.

In developed countries this transition began in the eighteenth century and

continues today.

Less developed countries began the transition later and are still in the earlier

stages of the model.

The world’s population has a certain evolution with different stages when the births and the deaths have different rates

However, all the countries aren’t in the same stage

That evolution of the population is the DEMOGRAPHIC TRANSITION MODEL

Every kind of country is in one of these stages throughout history

Poor developing countries are in the stage 2, less poor developing countries are in the stage 3, developed countries are in the stage 4 and, in the future, some developed countries will be in the stage 5

DEMOGRAPHIC TRANSITION MODEL

POPULATION STEADY

RAPID GROWTH OF

THE POPULATIONTHE GROWTH

OF THE POPULATION

IS LESS RAPIDTHE GROWTH

OF THE POPULATION IS

VERY SLOW, STEADY OR NEGATIVE

WHAT ARE THE STAGES OF POPULATION CHANGE?

THIS SEQUENCE IS CALLED “DEMOGRAPHIC TRANSITION MODEL”

STAGES OF THE DEMOGRAPHIC TRANSITION MODELSTAGE 1:

• Many births & Many deaths = Population is steady

• Until the Industrial Revolution

STAGE 2:

• Many births & death rate falls very fast = Very fast increase of the population

• Examples: The poorest developing countries (Nigeria, Kenya, Bangladesh, Afghanistan...)

STAGE 3:

• Birth rate falls & Death rate falls slowly = Rapid increase of the population

• Examples: The richest developing countries (Brazil, Mexico, India...)

STAGE 4:

• Birth rate is still falling & Death rate is still falling = Slow increase of the population

• Examples: The developed countries (European countries, USA, Japan...)

STAGE 5?

• Birth rate is still falling & Death rate is stable = Decrease of the population

• Examples:Italy, Sweden or Germany in the nearest future

Even if the World’s population has always increased, death rates have overcome the birth rates during some moments of the History in certain countries

BIG EPIDEMICS

Example: Bubonic plague in middle ages in Europe

WARS

Example: During the World Wars in some countries

NEW WAY OF LIFE IN WESTERN EUROPE ONE CHILD POLICY IN CHINA

WHY ARE SOME PLACES OVERPOPULATED?

Definition of overpopulated places:

They are the places where the number of people overweigh the availability of resources

The are two reasons to have an overpopulated place

Increase in population

Example: Bangladesh

Low resources

Example: Somalia