IBEnvironmental Systems & Societies (ESS)DPSLRevision NotesHuman Systems & Resource UseHuman Population DynamicsDemographic Variables

Syllabus Edition

First teaching 2015

Last exams 2025

|

Demographic Variables (DP IB Environmental Systems & Societies (ESS)): Revision Note

Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Bridgette Barrett

Updated on

Demographic Variables

  • Demographic tools are essential for understanding and quantifying human population dynamics

    • They provide valuable insights into birth and death rates, fertility patterns, population growth rates, and other demographic indicators

  • Below are some key demographic tools and how they are calculated:

Crude Birth Rate (CBR)

  • The CBR is the number of live births per 1 000 individuals in a population during a specific time period

  • It is calculated by dividing the total number of live births in a year by the total population and then multiplying by 1 000

CBR=total number of live births per yeartotal population×1 000

Worked Example

A country has 25 000 live births in a year, and the total population is 500 000.

Calculate the crude birth rate.

Answer

CBR = (Number of live births / Total population) x 1 000
CBR = (25 000 / 500 000) x 1 000
CBR = 50 births per 1 000 individuals

Crude Death Rate (CDR)

  • The CDR is the number of deaths per 1 000 individuals in a population during a specific time period

  • It is calculated by dividing the total number of deaths in a year by the total population and then multiplying by 1 000

CDR=total number of deaths per yeartotal population×1 000

Worked Example

In a given year, a country recorded 15 000 deaths, and the total population is 750 000.

Calculate the crude death rate.

Answer

CDR = (Number of deaths / Total population) x 1 000
CDR = (15 000 / 750 000) x 1 000
CDR = 20 deaths per 1 000 individuals

Total Fertility Rate (TFR)

  • The TFR is an estimate of the average number of children a woman would have during her reproductive years if she experienced the current age-specific fertility rates throughout her lifetime

  • It is calculated by summing the age-specific fertility rates (ASFR) and multiplying the result by five

TFR=ΣASFR×5

Worked Example

The age-specific fertility rates for a country are as follows:

Age 15-19: 20 births per 1 000 women
Age 20-24: 80 births per 1 000 women
Age 25-29: 120 births per 1 000 women
Age 30-34: 100 births per 1 000 women
Age 35-39: 40 births per 1 000 women
Age 40-44: 10 births per 1 000 women

Calculate the total fertility rate.

Answer

TFR = (20 + 80 + 120 + 100 + 40 + 10) x 5
TFR = 1 850 births per 1 000 women

Doubling Time (DT)

  • The DT is the time it takes for a population to double in size based on its current growth rate

  • It is calculated using the rule of 70, where the number 70 is divided by the population growth rate

DT=70growth rate %

Worked Example

A population has a growth rate of 2% per year.

Calculate the doubling time.

Answer

DT = 70 / Growth rate
DT = 70 / 2
DT = 35 years

Natural Increase Rate (NIR)

  • The NIR is the rate at which a population grows or declines due to the difference between the crude birth rate and the crude death rate

  • It is calculated by subtracting the CDR from the CBR and then dividing the result by 10

NIR equals fraction numerator CBR minus CDR over denominator 10 end fraction

Worked Example

A country has a CBR of 25 births per 1 000 individuals and a CDR of 10 deaths per 1 000 individuals.

Calculate the natural increase rate (annual growth rate).

Answer

NIR = (CBR - CDR) / 10
NIR = (25 - 10) / 10
NIR = 1.5%

  • These demographic tools provide valuable quantitative measures to analyse and compare population trends across different regions and time periods

  • They assist policymakers, researchers, and demographers in understanding population dynamics, projecting future growth, and formulating effective strategies for social and economic development

You've read 1 of your 5 free revision notes this week

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

  • I would just like to say a massive thank you for putting together such a brilliant, easy to use website.I really think using this site helped me secure my top gradesin science and maths. You really did save my exams! Thank you.

    Beth
    IGCSE Student

  • This website is soooo useful and I can’t ever thank you enough for organising questions by topic like this. Furthermore, the name of the website could not have been more appropriate as it literally did SAVE MY EXAMS!

    Fathima
    A Level Student
Test yourself

Did this page help you?

Previous:International Policy on Climate ChangeNext:Human Population Growth Curve
Author
Reviewer
Alistair Marjot

Author: Alistair Marjot

Expertise: Environmental Systems and Societies & Biology Content Creator

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

Bridgette Barrett

Reviewer: Bridgette Barrett

Expertise: Geography, History, Religious Studies & Environmental Studies Subject Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 30 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.

Download notes on Demographic Variables