When a population pyramid indicates that a country's population has a high percentage of young people, that usually means that the population is

Expansive

Explanation:

When a population pyramid indicates that a country's population has a high percentage of young people, that usually means that the population is expansive.

Expansive population pyramids show populations which have a higher percentage of people in younger age groups. Such populations with this shape usually have high fertility rates with lower life expectancies.

These types of populations usually represent the developing nations but some of the third world countries also have expansive population pyramids.