Understanding Stationary and Stable Populations

This question explores the definitions and relationships between two key demographic concepts: stationary population and stable population.

Analyzing the Statements

• Stationary Population: Age structure and total size remain constant. Birth rate equals death rate ($b=d$), and net migration is zero.
• Stable Population: Age structure remains constant, but the total size can change. Birth and death rates are constant but not necessarily equal ($b \neq d$).

Statement Breakdown:

• A. A stationary population is not always stable. This is false. A stationary population inherently has a constant age structure, meeting the definition of stable.
• B. A stationary population is always stable. This is true. Constant size and age structure satisfy the criteria for a stable population.
• C. A stable population need not be stationary. This is true. A stable population can grow or shrink if birth rates and death rates differ, while maintaining its age structure.
• D. In stationary population, the rate of overall change in the population is zero. This is true. By definition, a stationary population does not change in size. The rate of change is $\frac{dN}{dt} = 0$.
• E. In stable population, the rate of overall change in population is constant (not necessary zero). This is true. A stable population has constant birth and death rates, leading to a constant intrinsic rate of natural increase ($r = b - d$), hence a constant rate of change ($\frac{dN}{dt} = rN$). This rate ($rN$) is constant if $r$ is constant, but only zero if $r=0$.

Conclusion

Based on the analysis, statements B, C, D, and E are true.

The correct option is the one that includes B, C, D, and E.