Population concentration and density.

There are two basic properties of population--concentration and density. These are what geographers consider in studying the number of people and available resources in heavily populated areas and sparse areas. Two-thirds of the world's population is concentrated in four different regions: East Asia, South Asia, Southeast Asia and Western Europe. The rest is in sparsely occupied areas.

The heavily populated regions mentioned are similar through their proximity to or near rivers or water. They also are similar in that they are in fertile areas and temperate climates. Sparsely populated areas are too dry, wet, cold, or mountainous for activities such as agriculture.

Population density is the number of people occupying an area of land that can be computed in several different ways--arithmetic density, physiological density and agricultural density.
The arithmetic density is the number of people divided by the land area. The physiological density is a more meaningful population measure and is computed by looking at the number of people per area of a certain type of land. Agricultural density is the ratio of the number of farmers in the amount of arable land.

Population concentration and density therefore plays a major role in the geographer's study of population.