Per Capita Growth Rate

Per capita growth rate tells you how quickly a population changes per individual, which makes it easier to compare populations of different sizes. It is found by subtracting the death rate from the birth rate because each birth adds one individual and each death removes one, so the net change is births minus deaths. If births outnumber deaths, the population grows; if deaths outnumber births, it shrinks.

Use this formula in ecology, population biology, or demographic studies when you want a simple measure of whether a population is increasing or decreasing. It is especially useful for modeling bacteria, animal populations, or human populations when birth and death rates are given separately.

• Adding birth and death rates instead of subtracting death rate from birth rate
• Forgetting that r can be negative when death rate is larger than birth rate
• Confusing per capita growth rate with total population change, which depends on population size too