Which one of the following measures the natural growth rate of population?

Analyze the question: It asks which expression gives the natural growth rate of a population. The key word is "natural," which refers only to births and deaths. Migration is not included.

Concept:

• Natural growth rate (natural increase) = Birth rate − Death rate
• Total population growth = Natural increase + Net migration (immigration − emigration)

So migration affects total population change, but not the natural growth rate.

Evaluating the options:

• A. "Natural increase - Birth rate + Net migration" is muddled. It includes net migration and uses natural increase to define itself. ❌
• B. Birth rate − Death rate is exactly the definition of the natural growth rate. ✅
• C. Birth rate / Death rate is a ratio, not a difference, so it is not the standard measure. ❌
• D. "Birth + Net migration = Death" is an equation that describes no growth measure, and it includes migration. ❌

Example: If a country has a birth rate of 35 per 1,000 and a death rate of 12 per 1,000, the natural growth rate is 35 − 12 = 23 per 1,000, or 2.3%.

Exam tip: "Natural" means only births and deaths. If you see migration in an option, it is measuring total population change, not natural increase.