WEFOUNDpopulation history by state

Population density (in agriculture : standing stock and standing crop ) is a measurement of population per unit area or unit volume; it is a quantity of type number density . It is frequently applied to living organisms , and most of the time to humans . It is a key geographical term. [1]

Low densities may cause an extinction vortex and lead to further reduced fertility. This is called the Allee effect after the scientist who identified it. Examples of the causes in low population densities include: [2]

For humans , population density is the number of people per unit of area, usually quoted per square kilometer or square mile (which may include or exclude, for example, areas of water or glaciers). Commonly this may be calculated for a county , city , country , another territory or the entire world .