Fact 1: Population density is the average number of individuals per unit of area or volume.

Fact 2: Economy is affected by population size and density.

Given the two facts above, answer the question "What is affected by the average number of individuals per unit of area or volume?" with the following options: 
- goats
 - economy
 - cows
 - animals
 - vegetation
 - mammals
 - bushes
 - wind


 

  economy       