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Population Density and Distribution | ISC Class 12 Geography

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GeographyISC Class 12 · National and State Level Patterns of Population Distribution

Index of Concentration, Density and Distribution of Population (ISC Class 12)

Updated 17 October 2026 · Fact-checked

The index of concentration is a state's share of India's population: highest for Uttar Pradesh (about 16.5 per cent) and lowest for Sikkim (about 0.05 per cent). Arithmetic density is population per sq km of total area (India 382 in 2011); physiological density is population per sq km of net cultivated area. Distribution depends on landforms, climate, accessibility and level of development, with Bihar densest and Arunachal Pradesh sparsest among the states.

Understand Index of Concentration, Density and Factors of Population Distribution

1. Census. A census is the official, complete enumeration of a country's population at a fixed reference date. India's census is held every ten years, and the latest with results is that of 2011.

2. Index of concentration. As used in the syllabus, it is a state's share of India's total population expressed as a percentage. Formula: state population divided by India's population, times 100. In Census 2011 Uttar Pradesh is highest with about 16.5 per cent, followed by Maharashtra (about 9.3), Bihar (about 8.6), West Bengal (about 7.5) and undivided Andhra Pradesh (about 7.0); these five held almost half of India. The lowest among states is Sikkim, about 0.05 per cent. Rajasthan, the largest state by area (about 10.4 per cent of India), holds only about 5.7 per cent of the population, while Uttar Pradesh has about 7.3 per cent of the area and 16.5 per cent of the people.

3. Arithmetic density. Total population divided by total area, in persons per sq km. India had 382 in 2011 (325 in 2001).

4. Physiological density. Total population divided by net cultivated (net sown) area. It shows the pressure on the land that actually grows food. India's net sown area is about 140 million hectares, so physiological density is more than double the arithmetic density, roughly 850 to 870 persons per sq km of cultivated land. It is high where cultivable land is scarce, as in hilly states, and a rise over time signals pressure on farmland, smaller holdings and the need for intensive farming or non-farm jobs.

5. Extremes of density (2011). Highest state: Bihar, 1,106; then West Bengal (about 1,028) and Kerala (860). Lowest: Arunachal Pradesh, 17; then Mizoram (52) and Sikkim (86). Delhi had 11,320, the highest anywhere, and the Andaman and Nicobar Islands 46.

6. Density classes (arithmetic, 2011). High, above 500: the Ganga plain and delta, Kerala, the irrigated plains of Punjab and Haryana, Tamil Nadu (about 555). Moderate, 250 to 500: Jharkhand, Assam, Goa, Maharashtra, Tripura, Karnataka, Gujarat, undivided Andhra Pradesh and Odisha. Low, below 250: Madhya Pradesh, Rajasthan, Chhattisgarh, Uttarakhand, Himachal Pradesh, Jammu and Kashmir and the north-eastern hill states.

7. Factors of distribution.

  • Landforms: plains are flat and easy to farm, irrigate and build on (the Indus-Ganga-Brahmaputra plains and east-coast deltas are dense); mountains have steep slopes, thin soils and poor transport (the Himalayas and north-eastern hills are sparse, with people in valleys such as Kashmir and Imphal); plateaus are intermediate.
  • Climate: moderate humid climates with reliable rain attract people (Ganga plain, Kerala); the hot Thar Desert and cold Ladakh repel them, as does very heavy rain with dense forest.
  • Accessibility: roads, railways, ports and rivers draw settlement and industry; remote areas stay thin.
  • Level of development: industry and urban growth (Mumbai-Pune, the Hooghly belt, Delhi, Bengaluru), canal irrigation (Punjab, Haryana), mining (Chota Nagpur towns) and services raise density.

8. State comparisons. Bihar (1,106) and Arunachal Pradesh (17): a flat, watered alluvial plain with long farming against rugged, forested, heavy-rain, poorly connected mountains. Kerala (860) and Rajasthan (200): a humid coastal lowland with fertile soils against arid land with scarce water. Delhi (11,320) and the Andaman and Nicobar Islands (46): a metropolis against scattered forested islands.

Index of Concentration, Density and Factors of Population Distribution: key facts

Index of concentration
  • State population
  • divided by India's population
  • multiplied by 100
Arithmetic density
  • Total population
  • divided by total area
  • persons per sq km
Physiological density
  • Total population
  • divided by net cultivated area
  • persons per sq km of cultivated land
State extremes 2011
  • Bihar 1,106 highest
  • Arunachal Pradesh 17 lowest
  • Delhi 11,320
  • Andaman and Nicobar 46
Density classes
  • High above 500
  • Moderate 250-500
  • Low below 250 persons per sq km

How to answer Index of Concentration, Density and Factors of Population Distribution questions

For density questions, write the formula, substitute, include the unit, then interpret.

  1. 1Write the formula (arithmetic, physiological or index).
  2. 2Substitute the data with units and convert hectares to sq km if needed (100 hectares = 1 sq km).
  3. 3Divide and write the answer with its unit.
  4. 4Compare with the national figure or class limits.
  5. 5Give one physical and one economic reason.

Index of Concentration, Density and Factors of Population Distribution in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Why a hill village feels crowded despite low density

Suppose a hill district has a low arithmetic density because most of the land is steep forest, yet its families farm tiny terraces in a few valleys.

Which density measure better shows the crowding on its farmland, and why?

Try it first, then show the solutionSolution
  1. Physiological density divides the population by net cultivated area only.
  2. With little farmland in the valleys, this value is high even though the arithmetic density is low.

Answer: Physiological density, because it counts only the cultivated area.

Memory hook: Arithmetic counts all land; physiological counts only the farmed land.

Choosing a place to open a school

Suppose an education officer compares an irrigated plain district with a desert district for a new school and must justify where demand will be highest.

Use the factors of distribution to say which district is likely to be denser and why.

Try it first, then show the solutionSolution
  1. The irrigated plain has flat fertile land, water, roads and farming, which attract people.
  2. The desert district has scarce water and an extreme climate, which keep the density low.

Answer: The irrigated plain district is denser because of relief, water and accessibility.

Memory hook: Water, flat land and roads draw crowds.

Tricks to remember Index of Concentration, Density and Factors of Population Distribution

Short memory aids. Say each one aloud once, then use it on a question the same day.

  • UP, M, B, WB, AP

    Top five by share of population in 2011: Uttar Pradesh, Maharashtra, Bihar, West Bengal, undivided Andhra Pradesh.

    Use it when: Index of concentration.

  • Bihar up, Arunachal down

    Density extremes: Bihar 1,106 and Arunachal Pradesh 17 (states).

    Use it when: State extremes.

  • Physio-farm

    Physiological density divides by farm area; arithmetic by total area.

    Use it when: Density types.

Index of Concentration, Density and Factors of Population Distribution: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Index of concentration · 2 marks · Short answerBoard level

Name the state with the highest and the lowest index of concentration in Census 2011 and give the share of the highest.

Try it first, then show the solutionSolution
  1. Highest: Uttar Pradesh, about 16.5 per cent of India's population.
  2. Lowest: Sikkim, about 0.05 per cent.

Answer: Highest Uttar Pradesh (about 16.5 per cent); lowest Sikkim.

Example 2: Arithmetic density · 2 marks · Short answerBoard level

Invented figures: a state has a population of 8.4 crore and an area of 42,000 sq km. Find its arithmetic density and class (high, moderate or low).

Try it first, then show the solutionSolution
  1. Population = 8.4 crore = 84,000,000.
  2. Density = 84,000,000 / 42,000 = 2,000 persons per sq km.
  3. 2,000 is above 500, so it is high.

Answer: 2,000 persons per sq km; high.

Example 3: Physiological density · 4 marks · Long answerHarder board level

Invented figures: a state has a population of 6 crore, an area of 50,000 sq km and a net sown area of 20,000 sq km. Find its arithmetic and physiological density, and explain the difference.

Try it first, then show the solutionSolution
  1. Arithmetic density = 60,000,000 / 50,000 = 1,200 persons per sq km.
  2. Physiological density = 60,000,000 / 20,000 = 3,000 persons per sq km of cultivated land.
  3. The physiological value is higher because the denominator is only the cultivated area (20,000 sq km).
  4. It shows heavier pressure on farmland than the arithmetic figure.

Answer: Arithmetic 1,200 and physiological 3,000 persons per sq km; the second is higher because only net cultivated area is used.

Example 4: Population versus area share · 4 marks · Long answerHarder board level

Uttar Pradesh has about 7.3 per cent of India's area and 16.5 per cent of its population, while Rajasthan has about 10.4 per cent of the area and about 5.7 per cent of the population. Compare the two and explain the difference with two factors.

Try it first, then show the solutionSolution
  1. Uttar Pradesh: population share is more than twice its area share (16.5 / 7.3 is about 2.3), so it is very concentrated.
  2. Rajasthan: population share is about half its area share (5.7 / 10.4 is about 0.55), so it is thinly populated.
  3. Factor 1: the Ganga plain of Uttar Pradesh is flat, fertile and well-watered; Rajasthan has the Thar Desert and arid climate.
  4. Factor 2: long settled agriculture and good accessibility in Uttar Pradesh against scarce water and remoteness in the west of Rajasthan.

Answer: Uttar Pradesh's population share is about 2.3 times its area share; Rajasthan's is about 0.55 times, because of fertile plains and water against desert and aridity.

Example 5: Two-state comparison · 5 marks · Long answerHOTS / competency

Compare Kerala (860 persons per sq km) and Rajasthan (200) in 2011. State the density class of each, give one physical and one economic reason for each, and say whether the arithmetic density alone fully shows the pressure on Rajasthan's farmland.

Try it first, then show the solutionSolution
  1. Kerala 860 is above 500 (high); Rajasthan 200 is below 250 (low).
  2. Kerala physical: humid coastal lowland with fertile soils and two monsoons; economic: coconut and spice farming, fishing and remittances.
  3. Rajasthan physical: arid and semi-arid land with scarce water; economic: limited farmland and few industries over large areas.
  4. Arithmetic density counts the whole area including desert, so it understates the pressure on the small cultivated area; physiological density would show it better.

Answer: Kerala high (860) because of lowlands and cash crops; Rajasthan low (200) because of aridity; arithmetic density understates the pressure on Rajasthan's farmland.

Where students lose marks in Index of Concentration, Density and Factors of Population Distribution

The slips examiners see most often, and what to write instead.

  • Mistake: Using total area for physiological density

    The two densities are mixed up.

    Wrong working

    Physiological density = population / total area

    Right working

    Physiological density = population / net cultivated area

    Do this: Remember: physio means farm area.

    Usually costs: 1 to 2 marks.

  • Mistake: Quoting a union territory as the densest state

    Delhi is a UT; Bihar is the densest state.

    Do this: Say Bihar among states and Delhi among all regions.

    Usually costs: 1 mark.

  • Mistake: Naming a factor with no link to the pattern

    Answers say 'relief' without saying how relief affects settlement.

    Do this: Link each factor to a place and a result.

    Usually costs: 1 to 2 marks.

  • Mistake: Forgetting the unit

    Density is written as a bare number.

    Do this: Write persons per sq km.

    Usually costs: 1 mark.

Exam tips

  • Memorise the extremes: Uttar Pradesh and Sikkim for the index; Bihar and Arunachal Pradesh for density.
  • In a comparison, give figures, then one physical and one economic reason on each side.
  • Show the formula before substituting.
  • Keep growth rates and migration for their own topics.

Practice questions on Index of Concentration, Density and Factors of Population Distribution

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

  1. Q1 · 1 mark · MCQBoard level

    Physiological density is calculated by dividing the total population by the:
    (a) total area
    (b) net cultivated area
    (c) forest area
    (d) urban area

    Hint

    Land that grows food.

    Answer

    (b) net cultivated area.

  2. Q2 · 2 marks · Short answerHarder board level

    Invented figures: India's population is taken as 121 crore and a state has 6.05 crore. Find the state's index of concentration.

    Hint

    State divided by India, times 100.

    Answer

    6.05 / 121 x 100 = 5 per cent.

  3. Q3 · 4 marks · Long answerHarder board level

    Two regions have similar relief and climate, but one has railways, ports and mines and the other is remote. Explain how accessibility and level of development would make their densities differ, with two examples of development-led density.

    Hint

    Roads, ports, industry, irrigation, mining.

    Answer

    The connected region attracts settlement, trade and industry, so its density is higher; the remote region stays thin. Development raises density: canal irrigation turned Punjab and Haryana into dense farming regions, and mining around coal and iron ore built the towns of the Chota Nagpur plateau such as Dhanbad and Jamshedpur.

  4. Q4 · 3 marks · Short answerHarder board level

    Give three reasons why Arunachal Pradesh has a very low density while Bihar has a very high one.

    Hint

    Relief, forest and accessibility versus plain.

    Answer

    Arunachal Pradesh is rugged, densely forested, receives heavy rain and is poorly accessible (density 17). Bihar lies on the flat, watered alluvial Ganga plain with long settled agriculture (density 1,106).

  5. Q5 · 4 marks · Long answerHOTS / competency

    A student says: 'A state with a low arithmetic density cannot have a population problem.' Evaluate with the help of physiological density and an example of a type of state where the statement fails.

    Hint

    Hilly states with little farmland.

    Answer

    The claim is wrong. Arithmetic density spreads the people over all land, including forests, mountains and deserts. In a hilly state with little cultivable land the physiological density can be high, which shows heavy pressure on farmland, smaller holdings and a need for intensive farming or non-farm jobs.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

  1. 1.State with the highest index of concentration?Show answer

    Uttar Pradesh.

  2. 2.State with the lowest density in 2011?Show answer

    Arunachal Pradesh, 17.

  3. 3.Density of Delhi in 2011?Show answer

    11,320 persons per sq km.

  4. 4.High-density class limit?Show answer

    Above 500 persons per sq km.

  5. 5.Which density uses net cultivated area?Show answer

    Physiological density.

Index of Concentration, Density and Factors of Population Distribution: frequently asked questions

What is the index of concentration?

A state's percentage share of India's total population.

Why is Bihar so dense?

It lies on the flat, fertile, well-watered Ganga plain with long settled agriculture.

Why are mountain areas sparse?

Steep slopes, thin soil, cold climate and poor transport.

What is the density of India in 2011?

382 persons per sq km.