Explain the term growth rate of population.

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Detailed Solution

Population growth rate is how fast a population increases or decreases over time, usually shown as a percentage per year.

A population changes because of births, deaths, immigration, and emigration. When births and arrivals exceed deaths and departures, the population grows; otherwise it shrinks. We express this change per unit time to compare places and years.

Common formulas

Measure	Formula	Meaning
Crude growth rate	`r(%) = [(B − D)/N] × 100`	Births minus deaths as % of mid-year population
Net growth rate	`r(%) = [(B − D + I − E)/N] × 100`	Adds immigration (I) and emigration (E)
Instantaneous rate	`r = (1/N)(dN/dt)`	Used in ecology and exponential models

Interpretation

Positive r: Population is growing; age structure often younger.
Zero r: Stationary population; births balance deaths (after migration).
Negative r: Declining population; aging concerns, labor force issues.

Models

Exponential growth: When resources are abundant, N(t)=N₀e^{rt}.
Logistic growth: With limits, dN/dt=rN(1−N/K) where K is carrying capacity.

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