The fertility, mortality, and migration are crucial comes to the demographic picture of an area.
Explanation:
The population and its growth or decline depend on numerous parameters. Some of those parameters are the fertility, mortality, and migration. The fertility basically tells us how much children are born in a particular period. The mortality is telling us how much people have died in a particular period, while the migration is telling us is there people moving in or moving out of an area.
If the fertility rates are high and the mortality rates are high, the population will stagnate. If the fertility rates are high and mortality rates lower then the population will grow. If the fertility rates are lower and the mortality rates high then the population will be declining.
The migration rates can influence any of the previous scenarios though. If lot of people migrate into an area then the population of that area will be increasing. If there are mostly people moving out of the area then the population will be declining.
