Crude rates (AQA GCSE Statistics): Revision Notes
Crude rates
What are crude rates?
Crude rates are straightforward statistical tools that help us compare different population characteristics across groups or time periods. They're called "crude" because they provide a simple, basic way to make comparisons without complex adjustments.
These rates are particularly useful for comparing statistics like births, deaths, and employment levels between different populations, even when those populations are different sizes.
The basic formula
The fundamental structure for calculating any crude rate follows this pattern:
We multiply by 1000 to express the rate "per thousand people" rather than as a tiny decimal. This makes the numbers much easier to understand and compare.
Types of crude rates
Crude birth rate
This measures the number of births per thousand people in the total population.
Crude death rate
This measures the number of deaths per thousand people in the total population.
Crude unemployment rate
This measures the number of unemployed people per thousand of the total population.
Step-by-step calculation method
When working with crude rates, follow these steps:
- Identify what you're measuring - births, deaths, unemployment, etc.
- Find the number of events - the actual count of what happened
- Find the total population - the group you're comparing against
- Apply the formula - multiply the events by 1000, then divide by the population
- Round appropriately - usually to 1 decimal place
Worked examples
Let's look at some real examples to see how these calculations work in practice.
Worked Example 1: Unemployment rate calculation
In a town with a population of 63,400 people, 5,700 are unemployed. Let's calculate the crude unemployment rate:
Step 1: Identify the numbers
- Number unemployed = 5,700
- Total population = 63,400
Step 2: Apply the formula Crude unemployment rate =
Step 3: Calculate = = 89.9 per 1000 (to 1 decimal place)
This means there are approximately 90 unemployed people for every 1000 people in the population.
Worked Example 2: Age-specific birth rates
The table above shows birth data for England and Wales in 2016. Let's work through calculating crude birth rates for different age groups.
Part (a): Crude birth rate for mothers aged 30 to 34
The question asks for the rate per 1000 people in this specific age group.
Step 1: Identify the numbers from the table
- Number of births to mothers aged 30-34 = 220,129
- Number of women aged 30-34 = 1,966 thousand = 1,966,000
Step 2: Apply the formula Crude birth rate =
Step 3: Calculate = = 112.0 per 1000 (to 1 decimal place)
Part (b): Overall crude birth rate for females
Now we need the rate for the entire female population.
Step 1: Identify the numbers
- Total live births = 696,271
- Total female population = 29,546,000
Step 2: Apply the formula
Crude birth rate =
Step 3: Calculate = = 23.6 per 1000 (to 1 decimal place)
Important exam tips
Watch out for different rates Sometimes questions ask for rates "per hundred" instead of "per thousand". In these cases, multiply by 100 instead of 1000 in your formula.
Formula provided The exam question will usually give you the formula, but you still need to know how to apply it correctly.
Units matter Always check whether you're working with thousands, millions, or individual units. The table might show "1837 thousand" which means 1,837,000.
Round appropriately Most answers should be given to 1 decimal place unless the question specifies otherwise.
Practice opportunity
Try this calculation yourself: From October to December 2017, there were 32.15 million people employed in the UK and 1.47 million people unemployed. Work out the crude unemployment rate for the working-age population.
Hint: First find the total working-age population, then apply the standard formula.
Key Points to Remember:
- Crude rates help compare populations of different sizes by standardising to "per 1000 people"
- The basic formula is:
- Always check if you need the rate per hundred or per thousand
- Make sure you're using the correct population figure - sometimes it's age-specific or gender-specific
- Round your final answer to 1 decimal place unless told otherwise