Population: Distribution, Density, Growth and Composition

• Before 1921 (Phase I): India's population growth was erratic, stagnant, and stationary. High crude birth rates were canceled out by catastrophically high crude death rates caused by recurrent famines, bubonic plague, cholera, and malaria. The decade 1911–1921 recorded a negative population growth rate of $-0.31\%$ (the population contracted by 7.7 lakh people due to the 1918 Spanish Influenza pandemic).
• After 1921: Mortality rates began a sustained, permanent secular decline due to famine-relief railways and public health inoculations. The population never contracted again and grew continuously in every subsequent census. Hence, 1921 is universally termed the "Year of the Great Demographic Divide".

1. Crude Arithmetic Density: Total population divided by the total geographic area:

$$\text{Density} = \frac{\text{Total Population}}{\text{Total Geographical Area (sq km)}}$$

(India's average in 2011 was 382 persons/sq km).
2. Physiological Density: Total population divided by the net cultivated arable land area:

$$\text{Physiological Density} = \frac{\text{Total Population}}{\text{Net Cultivated Area (sq km)}}$$

3. Agricultural Density: Total agricultural population (cultivators + agricultural laborers and their families) divided by the net cultivated arable area:

$$\text{Agricultural Density} = \frac{\text{Agricultural Population}}{\text{Net Cultivated Area (sq km)}}$$

• Why More Useful: In an agrarian country like India, arithmetic density distorts reality by including vast uninhabitable deserts, barren rocks, and glaciated mountains. Physiological and agricultural densities reveal the true nutritional and human pressure exerted on the limited arable land that actually feeds the country.

During Phase III (1951–1981), India's population surged from 361 million to 683 million at an unprecedented annual growth rate of over 2.2%:
1. Precipitous Collapse of Mortality (Death Rate): Post-independence Five-Year Plans introduced modern antibiotics (penicillin, sulfa drugs), DDT vector control for malaria, and nationwide smallpox vaccination. The Crude Death Rate plummeted from 27 per 1,000 to under 15 per 1,000.
2. Stubbornly High Fertility (Birth Rate): Socio-cultural norms, universal early marriage, lack of contraceptive awareness, and the economic desire for children as agricultural labor kept the Crude Birth Rate high at nearly 40 per 1,000.
3. Large International Influx: Significant refugee migration from Tibet (1959), East Pakistan/Bangladesh (1971 war), Nepal, and Pakistan further amplified national numbers.

1. Indo-Aryan Family (Indo-European / Aryan): Accounts for 73% of India's population. Distributed across Northern, Western, and Central India. Includes Hindi, Bengali, Punjabi, Marathi, Gujarati, Odia, Assamese, and Urdu.
   2. Dravidian Family: Accounts for 20% of the population. Concentrated in Peninsular South India. Includes Telugu, Tamil, Kannada, and Malayalam.
   3. Austro-Asiatic Family (Nishada): Accounts for 1.38% of the population. Concentrated in the Chhota Nagpur Plateau (Jharkhand, Odisha, West Bengal) and Meghalaya. Includes Santhali, Mundari, Ho, and Khasi.
   4. Sino-Tibetan Family (Kirata): Accounts for 0.85% of the population. Concentrated along the Himalayan borderlands and the Northeast. Includes Bodo, Manipuri (Meitei), Mizo, and Ladakhi.

The Census of India classifies workers based on the number of days they engaged in economically productive work during the preceding 365 days:
• Main Worker: A person who engaged in economically gainful work for at least 183 days (or six full months) or more during the year. They represent the core, full-time employed workforce.
• Marginal Worker: A person who engaged in economically gainful work for less than 183 days (less than six months) during the year. They represent seasonal farm labor, underemployed casual workers, and part-time workers.

As per Census 2011, India's urban population stood at 31.16% (377 million people across 7,935 towns):
• Spatial Disparity: Urbanization is heavily concentrated along coastal industrial belts, mineral corridors, and transport nodes. The peninsular and western states show much higher levels of urbanization compared to the northern plains and northeastern states.
• Most Urbanized State: Goa is the most urbanized state with 62.17% of its population in urban areas, followed by Mizoram (52.11%) and Tamil Nadu (48.40%). (Among UTs, Delhi has 97.5%).
• Least Urbanized State: Himachal Pradesh is the least urbanized state with only 10.03% urban population (89.97% rural), followed by Bihar (11.29% urban).

• Northern Plains (UP, Bihar, West Bengal — Densities > 1,000/sq km):
1. Flat Topography: Deep, level alluvial plains formed by the Ganga-Brahmaputra river systems ideal for intensive canal irrigation and mechanized agriculture.
2. Water & Climate: Abundant perennial rivers, high groundwater tables, and favorable monsoon rainfall.
3. Infrastructure: Dense networks of roads, railways, and historic trading urban centers.
• Northeastern States (Arunachal Pradesh — 17/sq km):
1. Rugged Mountainous Terrain: Steep slopes, dense jungle, and shallow acidic soils impede farming.
2. Inaccessibility: Frequent landslides, seismic activity, and severe lack of transport and industrial infrastructure.

India is a secular nation with a diverse religious tapestry:
1. Hindus: 79.8% of the total population, forming the major religious group in almost all states (except J&K, Punjab, and three NE states).
2. Muslims: 14.2%, the largest religious minority, with major concentrations in Jammu & Kashmir, Lakshadweep, West Bengal, Kerala, and Uttar Pradesh.
3. Christians: 2.3%, concentrated mainly along the Western coastal belt (Goa, Kerala) and the Northeastern states (Nagaland, Mizoram, Meghalaya).
4. Sikhs: 1.7%, heavily concentrated in Punjab (where they form a majority) and neighboring Haryana and Delhi.
5. Buddhists (0.7%) (Maharashtra, Ladakh, Sikkim) and Jains (0.4%) (urban centers of Rajasthan, Gujarat, and Maharashtra).