Calculating population change…

What factors do you need to take into account when calculating population growth?

Population dynamicsLearning outcomes

You should all be able to:Identify the different factors that affect a change in population size.

Most of you should be able to:Calculate “crude birth rate, crude death rate, fertility, doubling time and natural increase rate”.

Some of you might be able to:Explain different values of “crude birth rate, crude death rate, fertility, doubling time and natural increase rate” from given data.

Measure of population change

• Crude birth rate • Crude death rate• Fertility• Doubling rate• Natural increase rate

Crude Birth Rate

Calculate the following CBR:USA, 2005 Births: 4,138,349Total population: 295,895,897CBR = ? 13.98 per thousand

Total number of birthsTotal population X 1000CBR =

What is Crude Birth Rate?

The number of live births per 1000 people in a population. It does not take into account the age and sex structure of the population.

Crude Death Rate

• How do you think it is calculated?

Total number of deathsTotal population X 1000CDR =

Calculate the following CDR:USA, 2005 Deaths: 2,448,017Total population: 295,895,897CDR = ? 8.27 per thousand

Fertility Rate

Total Fertility Rate is the average number of children each woman has over a lifetime.

Fertility Rate is the number of births per thousand women of child-bearing age.

Sometimes used as a synonym for birth rate. However fertility rate focuses on the number of births per 1000 women and birth rate looks at the entire population.

Total number of birthsNumber of women of child-bearing age

X 1000Fertility rate =

Natural Increase Rate

The difference between the number of live births and deaths occurring in a year.

Measures the population change but does not include the effects of migration.

How would you calculate this?

Crude Birth Rate – Crude Death Rate10

NIR % =

What was the NIR for the USA in 2005?

0.57%(13.98 – 8.27) = 10

Doubling Time

70Natural Increase RateDoubling time (years) =

The time in years that it takes a population to double.

If you have an NIR of 1% what will the doubling time be?

What was the doubling time of the US in 2005?70 / 0.57 = 122.8 years

On the worksheet

Fill in the blank spaces using the calculations that we have just seen.