When calculating population growth, which of the following equations is appropriate?

Question

When calculating population growth, which of the following equations is appropriate?
A. (Emigrants-immigrants)+ (births-deaths)
B. (Immigrants-emigrants)+ (births -deaths)
C. (Births+ deaths)-(emigrants + immigrants)
D. (Births-deaths) -(immigrants+ emigrants)

 

Is it B 

Answer 1

To illustrate, let's say your current population is P = 100.  In one year, you get:

 

Emigrants = 20        20 people leave, so P = 100 - 20 = 80

Immigrants = 15      15 new people arrive, so P = 80 + 15 = 95

Births = 10               10 new children are born, so P = 95 + 10 = 105

Deaths = 5                5 people die, so P = 105 - 5 = 100

 

A.  (20-15)+(10-5)= 5 +5 = 10            A net gain of 10 people, P = 110

B.  (15 -20)+(10-5) = -5 + 5 = 0          A net gain of 0 people, P = 100

C.  (10+5)-(20+15) = 15 - 35 = -20     A net loss of 20 people, P = 80

D.  (10-5)-(20+15) = 5 - 35 = -30        A net loss of 30 people, P = 70

 

B is the answer because Immigrants and Births are additions to the population, Emigrants and Deaths are subtractions.