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Module 7 Population Distribution and Its%u00a0Consequences 111Arithmetic or Crude DensityOften used interchangeably with population density, arithmetic (crude) density is the average number of people per unit of land area (usually per square mile or kilometer). It is the most commonly used measure of population density and can be calculated by dividing the total population of a country (or place) by its corresponding land area. The higher the result, the more crowded a country is. In mid-2022, the world population was 7963 million, and Earth%u2019s total land surface is 57.51 million square miles (148.94 million square kilometers). We calculate the arithmetic density for the whole world as follows:7963 %u00f7 57.51 = 138 persons per square mile7963 %u00f7 148.94 = 53 persons per square kilometerThe very uneven population distribution on Earth has created huge disparities in density. Refer back to Figure 7.1 to see how one end of the spectrum contains densely settled in parts of East Africa, a form of sleeping sickness known as nagana attacks livestock. That disease is almost always fatal to cattle but not to humans. The people in this part of East Africa depend heavily on cattle, which provide food, represent wealth, and serve a religious function in some tribes. The spread of this disease by tsetse flies has caused entire tribes to migrate away from infected areas, leaving those areas unpopulated.Methods for Calculating Population Density7-3 What are the three methods for calculating population density?Identifying population distribution patterns is useful, but it does not tell us how crowded a place is and how population size compares with available natural resources, particularly land. To better understand the relationship between population and environment, geographers use the concept of population density, or the average number of people per unit of land area (Figure 7.10). Three population density indicators measure the ratio of population size to land area: arithmetic or crude density, physiological density, and agricultural density.(a) (b)Figure 7.10 Comparison of densely populated and sparsely populated areas. Population density varies considerably on Earth%u2019s surface as seen in the (a) densely populated city of Hong Kong versus (b) a sparsely populated rural area in the United States. (a) ymgerman/iStock/Getty Images; (b) ClassicStock/Getty ImagesTERMS TO KNOWpopulation density: The average number of people per unit of land areaarithmetic (crude) density: The average number of people per unit of land area (usually per square mile or kilometer)%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.