Beginners:Population

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This article is part of Statistics 4 beginners, a section in Statistics Explained where statistical indicators and concepts are explained in an simple way to make the world of statistics a bit easier both for pupils and students as well as for all those with an interest in statistics.

Why is information about the number of people living in a country, a region or a town needed? Governments, for example, need to know how many inhabitants currently live in the country and how many there will be in the future. From this they can plan and make better decisions regarding the construction of schools, hospitals, roads etc. Governments also need to know how old the population is and will be in the coming years in order to plan for pensions, health care etc.

Watch the video explaining the population change


Full article

How is the population in a country or given area calculated?

The population of a given area is defined as the number of people usually living in that area, measured on 1 January in a given year. The source can be the most recent population census (a census is when the population is counted). Since a census is normally carried out every 10 years, a yearly adjustment has to be made in order to get the population number for a specific year. This adjustment consists of the natural population change and the net migration. The natural population change is calculated by births minus deaths and net migration is the number of immigrants (population moving into the country) minus the number of emigrants (population moving out of the country) - please see example below. In some countries population registers are used instead.

Example

In the EU on 1 January 2016, the population was estimated at 510 million compared with 508 million on 1 January 2015. This means that the population grew by 2 million persons during the year 2015. Was this due to natural population change or net migration? As 5.1 million babies were born and 5.2 million persons died, there was a negative natural population change (-0.1 million). The net migration was therefore the reason for the increase.

What other important indicators about the population are used?

Some examples:

The fertility rate is the average number of children born alive to a woman taking into consideration current fertility rates. The definition of a birth is the start of life when a child emerges from the body of its mother. The crude birth rate is defined as the number of births during the year divided by the population in that year; the value is expressed per 1 000 persons.

Example

In 2014, 5.1 million children were born in the EU, corresponding to a crude birth rate of 10.1 births per 1 000 persons. This rate has decreased: it was 10.6 in 2000, 12.8 in 1985 and 16.4 in 1970. Among the EU Member States, France reported the highest fertility rate in 2014, with 2.01 live births per woman and the lowest fertility rate was recorded in Portugal (1.23 live births per woman).

How long is a person expected to live? This is measured through the indicator life expectancy. It can be expressed as the life expectancy at birth, which is the number of years a new-born baby can expect to live. The calculation of life expectancy takes into account the mortality conditions today; resulting in how likely it currently is to die at each age. The life expectancy is normally calculated for the total population and also separately for women and men. Life expectancy for women is generally higher than for men.

Example

Over the past 50 years, life expectancy at birth has increased by about 10 years for both men and women in the EU. This means that a baby born in 2014 is expected to live 80.9 years, reaching 83.6 years for a baby girl and 78.1 years for a baby boy, while it was around 10 years less around 1960.

The crude death rate is defined as the number of deaths during a year divided by the population in that year; the value is expressed per 1 000 persons. Infant mortality is the death of a child aged less than one year. The infant mortality rate is defined as the number of deaths of children under one year of age during a year divided by the number of live births in that year; the value is expressed per 1 000 live births.

Example

In 2014, some 4.9 million persons died in the EU, which corresponds to a crude death rate of 9.7 per 1 000 persons. This rate remained more or less the same over the last 40 years, with a maximum in 1993 with 5.0 million deaths, which corresponded to a crude death rate of 10.5 per thousand persons.

Population pyramid

A population pyramid is a graphical illustration which helps to visualise the number of persons by age group for a certain year; it can look like this:

Population pyramids, EU-28, 2001 and 2015
(% of the total population)

Source: Eurostat (demo_pjangroup)

Population-pyramid.gif

See the animation above and the text below for an explanation
The oldest age group is on top, the youngest at the bottom; men are usually on the left side, women on the right. In the illustration above, 2001 (with a border) and 2015 (solid colours) are compared. We can see that in 2015, the age group with the highest share of the population was those aged 45-49, while in 2001 it was the age groups 30-34 and 35-39. From the shape of the pyramid, we can see that the population is getting older as the younger age groups are decreasing and the older ones increasing. This can also be illustrated by the median age of the population: in 2015 it was 42.4 years, while in 2001 it was 38.3 years.

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