Population Density refers to a ratio between population and land area in a country. Types of population density:
1. The arithmetic population density: In this the number of people is divided by the total land area. It is the simplest method to understand the degree of concentration of population. Although density ignores differences in population distribution within a country or region taken, it is still a better method to compare population characteristics of the countries. For example, in 2011, the United States population density was relatively low, about 34.1 persons per sq. km while United Kingdom had a population density of 259.4 persons per sq. km.
2. Physiological or nutritional density: It is a more refined method of calculating man-land ratio. It is the number of people per unit area of arable land physiological density reflects the intensity of agriculture. In nearly all the populous developing countries in Asia-including India, Indonesia, Pakistan and Bangladesh, there is less than one acre (0.4 hectare) of cropland per person. Exactly, in India 1 hectare of cultivated or cropland supports 5 persons. In China, each hectare of cropland supports 12 persons, while in USA it is only 1.5 persons per hectare.