Population data can be plotted and described or interpreted in a couple of ways depending upon its purpose. For finding out a broad distribution pattern, population is collected and plotted on the basis of large units like states or their major parts.
If information is needed for more accurately, the smaller units like districts or even tehsils are used.
On the basis of availability of state level data, the density of population in India can be broadly divided into three zones: the areas of high density, the areas of moderate density and the areas of low density.
The areas having a density of population of more than 400 persons per square kilometre are included in this category. These areas have a high density due to fertile land and high amount of precipitation e.g. Kerala, West Bengal and Tamil Nadu. In these regions, a larger number of people can be provided sustainence per unit of area due to availability of fertile land which can produce more food for a large number of people.
But the situation is entirely different in the case of Union Territories like Delhi, Chandigarh and Pondicherry. These regions are highly urbanised and offer job opportunities in industrial and service sectors. Thus, the areas having fertile soil and those having good employment opportunities are densely populated.
States and Union Territories in which the density of population ranges between 100 and 400 persons per square kilometre are called areas of moderate density of population. They are Andhra Pradesh, Assam, Dadra & Nagar Haveli, Goa, Gujarat, Karnataka, Madhya Pradesh, Maharashtra, Orisa, Rajasthan, Tripura, Jharkhand, Chhattisgarh, Jammu and Kashmir, Uttarakhand, Himachal Pradesh, Nagaland, Manipur and Meghalaya. This region includes largest part of the country in terms of area.
Moderate density of population is characterised by the areas in which the agriculture is handicapped by rugged topography, lower amount of precipitation and paucity of water for irrigation. The scope for developing primary and secondary activities is quite large if the facilities are provided in this area.
For example, at the time of independence Chhotanagpur region was a sparsely populated area but development in the field of mining and industries in this part of the country has been mainly responsible for moderate density of population in this region.
All the remaining parts of India having a density of population less than 100 persons per square kilometre may be classified under this category. The States and Union Territories falling under this category include Arunachal Pradesh, Mizoram, Sikkim and Andaman and Nicobar Islands.
Low density population areas are characterised by rough terrain, low rainfall or unhealthy climate. Due to the above reasons the prospects of earning livelihood is low in these areas. Agriculture cannot be developed in too dry or cold areas. Uneven topography and poor agricultural resources put a limit on urbanisation and industrialisation. Therefore, the number of persons that can be supported per unit area is low in such regions. Difficulties exist not only in transport and communication in the hilly and mountainous areas but also in the over all levels of economic development. That is why the density of population in all these areas is low.