1. 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?

2. 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

3. There are other important factors to know and predict the growth of the population
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
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 by
Number 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?

4. 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?

5. 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.

6. 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
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
That evolution of the population is the DEMOGRAPHIC TRANSITION MODEL

7. DEMOGRAPHIC TRANSITION MODEL

8. POPULATION
STEADY
RAPID
GROWTH OF
THE
POPULATION
THE GROWTH
OF THE
POPULATION
IS LESS RAPID
THE GROWTH
OF THE
POPULATION IS
VERY SLOW,
STEADY OR
NEGATIVE

9. WHAT ARE THE STAGES OF POPULATION CHANGE?
THIS SEQUENCE IS CALLED “DEMOGRAPHIC TRANSITION MODEL”

10. STAGES OF THE DEMOGRAPHIC TRANSITION MODEL
STAGE 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

11. 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

12. 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