Census concepts

1. Meaning, administration and enumeration

A census seeks to enumerate every person in a specified territory rather than estimate population characteristics from a sample. Its essential features are individual enumeration, universality within a defined territory, a common reference time and periodicity. India traditionally conducts its population census every ten years. Census 2011 remains the latest completed decennial census; the exercise scheduled for 2021 was postponed.

The Office of the Registrar General and Census Commissioner, India, under the Ministry of Home Affairs, administers the exercise through state and Union Territory census directorates and field personnel. The Census Act, 1948 provides the legal framework, including obligations to answer prescribed questions and safeguards for individual census records. Published tables provide aggregate information; individual returns are not open to ordinary public inspection.

The exercise generally has two major stages. Houselisting and Housing Census records buildings, census houses, households, amenities and assets. Population Enumeration collects demographic, social and economic particulars of individuals. A household generally comprises people who normally live together and take meals from a common kitchen, unless work prevents this. Members need not be related. Institutional households, such as hostels and prisons, and houseless households receive separate treatment.

The census reference moment is distinct from the period during which enumerators visit households. For most of India, Census 2011 used 00:00 hours of 1 March 2011 as its reference moment. A revisional round accounted for relevant births, deaths and movements. Snow-bound areas had special schedules. De facto enumeration counts people where they are found, whereas de jure enumeration associates them with usual residence; actual census instructions specify how residents, visitors and absentees are handled.

• A census is not a sample survey: it provides detailed small-area counts, although omissions and classification errors can still occur.
• A census house is a physical unit; a household is a living arrangement. One building or census house may accommodate multiple households.
• Enumeration covers persons according to residence rules, not merely citizens; the population census is not a citizenship register.

2. Rural–urban classification and settlement concepts

Census classification distinguishes statutory towns from census towns. A statutory town is a place with a municipality, municipal corporation, cantonment board, notified town area committee or comparable statutory urban authority. Its recognition follows its legal-administrative status; it need not independently satisfy all numerical criteria for a census town.

Under Census 2011 criteria, a census town must satisfy three conditions simultaneously: a minimum population of 5,000; at least 75 per cent of its male main working population engaged in non-agricultural pursuits; and a population density of at least 400 persons per square kilometre. The occupational criterion does not refer to all residents, all workers or all male workers. A census town may remain governed by a gram panchayat despite being statistically urban.

An urban agglomeration is a continuous urban spread comprising a town and its adjoining outgrowths, or two or more physically contiguous towns with or without outgrowths. Under the 2011 framework, it must contain at least one statutory town, and the combined population of its constituents should not have been below 20,000 in the preceding census. Outgrowths are identifiable areas with urban characteristics adjoining a town, such as railway colonies, university campuses or port areas.

Urbanisation means an increase in the urban share of total population, not simply an increase in the number of urban residents. Urban growth can result from natural increase, net migration, settlement reclassification and boundary expansion. Therefore, an increase in the urban population cannot automatically be attributed entirely to rural-to-urban migration.

• Places not classified as urban are treated as rural for census purposes.
• Class I towns have a population of at least 100,000; a million-plus city or urban agglomeration has at least one million people.
• Administrative city boundaries and the wider continuous urban spread may produce different population totals.

3. Population size, growth, density and sex composition

Absolute population growth is the difference between population counts at two dates. Decadal percentage growth equals this difference divided by the population at the beginning of the decade, multiplied by 100. It is not an annual growth rate. Census 2011 recorded approximately 17.7 per cent growth during 2001–2011.

Population density is population divided by geographical area, expressed in persons per square kilometre. India’s 2011 density was 382. Bihar had the highest density among states, at 1,106, whereas Arunachal Pradesh had the lowest, at 17. State rankings should not be confused with rankings that include Union Territories. Density alone does not measure crowding, resource pressure or quality of life because settlement patterns and resource availability differ.

In Indian census usage, sex ratio means females per 1,000 males. The overall sex ratio was 943 in 2011. Child sex ratio refers specifically to girls per 1,000 boys in the 0–6 age group and stood at 919. Neither should be confused with sex ratio at birth, which relates female live births to male live births during a specified period.

Population change reflects births, deaths and net migration, while boundary changes can affect comparisons between administrative units. Age composition helps assess demographic dividend, ageing and dependency. Dependency ratios compare dependent-age populations with working-age populations, but age bands must always be specified. An age-based dependency ratio does not establish whether an individual actually earns an income.

• A falling growth rate can coexist with a large absolute population increase.
• Use comparable territorial boundaries when comparing districts or states across censuses.
• Avoid mixing final 2011 figures with provisional values, such as the initially reported overall sex ratio of 940.

4. Literacy, workers and migration

A literate person is someone aged seven years or above who can both read and write with understanding in any language. Formal schooling or a certificate is unnecessary. A person who can only read is not counted as literate. Children below seven are excluded from the denominator of the effective literacy rate, regardless of their actual abilities. Final Census 2011 figures placed literacy at approximately 73.0 per cent, compared with the widely quoted provisional estimate of 74.04 per cent.

Census work means participation in economically productive activity, with or without compensation, wages or profit. It includes relevant unpaid work on a family farm or enterprise. Main workers worked for six months or more during the reference year; marginal workers worked for less than six months. Non-workers did not participate in such economic activity. Unpaid household duties within one’s own household are not classified as census economic work.

Workers are grouped into cultivators, agricultural labourers, household industry workers and other workers. Cultivators cultivate land owned or held from others, including through supervision; agricultural labourers work on another person’s land for wages and do not bear cultivation risk. Work participation rate is total workers, including main and marginal workers, divided by total population, multiplied by 100.

Migration tables use place of birth and place of last residence, which identify different migrant populations. They also record duration of residence and reasons such as employment, education, marriage and movement with the household. Rural–rural, rural–urban, urban–rural and urban–urban streams must be distinguished. Seasonal mobility can be difficult to represent fully through a residence-based census snapshot.

• Literacy rate is not the same as school enrolment, educational attainment or functional skill level.
• Main worker does not necessarily mean a permanent salaried employee.
• Census work participation rate is not interchangeable with labour-force participation or unemployment rates from the Periodic Labour Force Survey.

5. Uses, related datasets and examination cautions

Census data support settlement planning, infrastructure provision, disaster preparedness, welfare targeting and analysis of regional inequalities. They provide a benchmark for population projections and sampling frames. However, census counts are periodic snapshots; projections for later years must not be presented as fresh enumerations.

The Civil Registration System continuously registers births and deaths. The Sample Registration System generates demographic estimates through a sample-based dual-record system. The National Family Health Survey measures health, nutrition and related demographic indicators through household samples. These sources complement, rather than replace, the census.

The Socio Economic and Caste Census 2011 was a separate exercise and should not be confused with the decennial population census. Similarly, an electoral roll covers eligible registered voters, not the entire population. For examination answers, identify the source, reference year, age group, denominator and territorial unit before interpreting any statistic.

• Population totals cannot by themselves explain development: examine age, education, occupation and spatial distribution.
• Changes in definitions and boundaries can limit direct comparisons across datasets and years.

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