The physiological density or real population density is the number of people per unit area of arable land . 
A higher physiological density suggests that it is possible to use a lower bound to have a lower physiological density.
Population density is a measure of the number of people in an area. It is an average number. Population density is calculated by dividing the number of people by area. Population density is usually shown as a number of people per square kilometer.
The result shows that the United States has an arithmetic density of 30 persons per square kilometer (78 person per square mile). By comparison, the arithmetic density is much higher in South Asia. In Bangladesh, it is approximately 1,020 persons per square kilometer (2,640 person per square mile) and 325 (480) in India.
- Population density
- List of countries by physiological density
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