Physiological density

Topic: Population of India: Distribution, Density, Growth and Composition · NCERT: Class 12, Ch 1 "Population: Distribution, Density, Growth and Composition"

Meaning

Physiological density is the total population of an area divided by its net cultivated area (the land actually sown with crops). It counts how many people, farm and non-farm, depend on each unit of cropland.

It matters because India is an agricultural country. The usual arithmetic density divides people by all land, including deserts, forests and mountains, so it can hide how crowded the food-growing land really is. Physiological density shows that hidden crowding.

Explanation

How it is calculated

• Formula: Physiological density = total population ÷ net cultivated area.
• Numerator (top number): the total population, meaning everyone, whether they farm or not.
• Denominator (bottom number): net cultivated area, also called net sown area.
• This is the land actually sown with crops in a year.

• A plot sown twice in one year is still counted only once.

• How to read it:

• High physiological density: each hectare of cropland must feed many people, so pressure on farmland is strong.
• Low physiological density: each hectare of cropland supports fewer people.

Why it is needed: the weakness of arithmetic density

• Arithmetic density = total population ÷ total area (sq km). It is a crude measure (a rough one), because it treats every sq km the same: fertile plain, desert, forest or snow-covered mountain.
• The problem it creates:
• Arunachal Pradesh has the lowest arithmetic density, 17 persons per sq km (Census 2011). However, most of its land is mountain and forest.
• Its small area of farmland may still be crowded.

• A desert state and a fertile delta can show similar arithmetic density but face very different pressure on their food-growing land.

• The fix: physiological density divides people only by the land that actually grows crops.

Key rules to remember

• It is always higher than arithmetic density.
• Net cultivated area is always smaller than total area.

• Dividing the same population by a smaller area gives a bigger number.

• The gap between the two is widest where little land can be farmed.

• Hill states have steep slopes, forests and poor soil. Their arithmetic density can look moderate or low, but their physiological density can be very high.

• Kerala has little flat land, so the pressure on its cropland is also very high.

• Its limit: it does not separate farm and non-farm people. A city worker and a farmer count the same. Agricultural density fixes this.

Where the data comes from

• The population figure comes from the decennial Census (one held every 10 years).
• Census 2011 was the last census held. The census due in 2021 was postponed because of the COVID-19 pandemic [2]. So Census 2011 figures are still the latest official ones.
• Census 2027 will be India's first digital census, with geo-referenced jurisdictions (each enumeration area is linked to its place on the map) [2]. It will give updated population data for working out density ratios.

Where it occurs

• India as a whole: NCERT uses it alongside arithmetic density because a large share of Indians depend on farming. India's arithmetic density rose from 117 (1951) to 382 persons per sq km (2011). The land area stayed the same, so the pressure on cropland also grew.
• Himalayan states and north-eastern hill states (except Assam): low arithmetic density, but only a small share of the land can be farmed. This pushes physiological density up.

• Arunachal Pradesh has the lowest arithmetic density at 17, but most of its land is mountain and forest.

• Kerala (south-west coast): high arithmetic density (859) and little flat land, so the pressure on cropland is very high.

• Ganga plain: Bihar (1,102; final 1,106), West Bengal (1,029), Uttar Pradesh (828). These states have very high populations on fertile alluvial land, so the pressure on cropland is also heavy.
• NCT of Delhi (11,297) and other mostly urban UTs: most people do not farm and there is very little cropland. This shows the measure's weakness: it mixes farm and non-farm people.

Don't confuse with

• Arithmetic density: total population ÷ total area. Physiological density uses net cultivated area as the denominator, so it is always the higher figure.
• Agricultural density: agricultural population (cultivators + agricultural labourers + their families) ÷ net cultivable area. Physiological density uses the total population. Do not swap the numerators.
• Net cultivated (net sown) area vs gross cropped area: physiological density uses net sown area, where a plot sown twice in a year is counted only once.

Prelims Hooks

• Physiological density = total population ÷ net cultivated area. It is always higher than arithmetic density.
• Trap: "Physiological density = agricultural population ÷ net cultivable area" is wrong. That is the formula for agricultural density.
• Net sown area: land sown at least once in a year, counted only once even if it is sown more than once.
• Physiological density measures the pressure of all people, farm and non-farm, on cropped land. It does not separate farmers from non-farmers.
• Hill states and Kerala: little flat land, so physiological density is very high compared with their arithmetic density.
• Arunachal Pradesh (17) has the lowest arithmetic density, but this low figure hides pressure on its small farmed area.

Mains Points

• Better measure than arithmetic density (GS-I): arithmetic density is crude because it ignores land quality. Physiological density links people to the land that actually feeds them, which matters more in agricultural India. It shows real pressure in hill states and Kerala, where farmland is scarce, that arithmetic density hides.
• Effects of high pressure on cropland:
• Small holdings and land fragmentation (land split among heirs into tiny, scattered plots).
• Disguised unemployment (extra family members working on a farm without adding to output), as in Bihar and the eastern Ganga plain.
• Out-migration from Bihar and Uttar Pradesh to Punjab, Delhi and Maharashtra.

• Policy responses include land consolidation, non-farm rural jobs, agro-processing and skilling.

• Data gap: with Census 2021 postponed, density ratios still use 2011 data. The digital, geo-referenced Census 2027 (Houselisting in April–September 2026, Population Enumeration in February 2027) will allow fresh and more detailed calculations for planning [2][3].

Related concepts

• Population density
• Agricultural density

Read more

• Density of population: arithmetic, physiological and agricultural