The correct option is
C. birth rate minus death rate.
Detailed Explanation:
- Understanding Natural Growth Rate:
- The natural growth rate of a population refers to the change in population size that occurs due to the difference between the number of births and the number of deaths in a given period, typically expressed as a percentage of the total population.
-
It does not take into account migration (people moving in or out of a population), which is why it is termed "natural."
-
Formula for Natural Growth Rate:
- The formula to calculate the natural growth rate (NGR) is:
[
\text{NGR} = \text{Birth Rate} - \text{Death Rate}
]
-
Here, the birth rate is the number of live births per 1,000 people in a year, and the death rate is the number of deaths per 1,000 people in a year.
-
Why Option C is Correct:
- Option C correctly identifies that the natural growth rate is derived from subtracting the death rate from the birth rate. This calculation gives us the net increase or decrease in population due solely to natural factors (births and deaths).
- For example, if a country has a birth rate of 20 per 1,000 and a death rate of 10 per 1,000, the natural growth rate would be:
[
\text{NGR} = 20 - 10 = 10 \text{ per 1,000}
]
- This means the population is growing at a rate of 10 people per 1,000 due to natural factors.
Why the Other Options are Incorrect:
- Option A: Sum of the birth rate and the death rate:
-
This option is incorrect because it suggests that the natural growth rate is the total of births and deaths, which does not reflect the actual change in population size. Instead, it would give a misleading figure that does not indicate whether the population is growing or shrinking.
-
Option B: Sum of the birth rate and the net migration rate:
-
This option is also incorrect because it includes net migration, which is not part of the natural growth rate. The natural growth rate focuses solely on births and deaths, while net migration accounts for people moving in and out of the population, which is a different concept.
-
Option D: Birth rate divided by the net migration:
- This option is incorrect as it suggests a division operation that does not relate to how we calculate the natural growth rate. The birth rate divided by net migration does not provide meaningful information about population growth and is not a standard calculation in demographic studies.
Common Pitfalls:
- Students often confuse the natural growth rate with overall population growth, which includes migration. It’s important to remember that "natural" refers only to births and deaths.
- Misunderstanding the definitions of birth rate and death rate can lead to incorrect calculations. Always ensure you are using the correct figures and understand what they represent.
Revision Summary:
- The natural growth rate is calculated as the birth rate minus the death rate.
- It reflects the change in population size due to natural factors only, excluding migration.
- Correct understanding of terms is crucial to avoid confusion with overall population growth.
- Always use the correct formula: NGR = Birth Rate - Death Rate.