Introduction and Sources of Population Data
What it is
Population Studies examines the size, distribution and composition of populations and the births, deaths and migration that change them. Unit I covers the discipline's scope, the institutions behind demographic behaviour, the growth of world and Indian population, and above all the data. Every later measure rests on these sources, so UGC-NET tests both their history and the indices that judge their quality.
Core concepts
History, definition, nature and scope. John Graunt's Natural and Political Observations … upon the Bills of Mortality (1662) founded the field, making Graunt the father of demography; Edmond Halley built the first scientific life table from Breslau data (1693), and Achille Guillard coined "demography" (1855). Hauser and Duncan's The Study of Population (1959) defined demography as the study of the size, territorial distribution and composition of population, changes in them, and the components of change. They separated formal demography (the population variables alone) from population studies (their links with social, economic, biological and environmental variables). The balancing equation: Pt = P0 + B − D + I − E, with B − D the natural increase and I − E net migration.
Social structure, culture and institutions. Culture makes son preference and early, near-universal marriage "normal". Marriage is the main exposure to childbearing in India, so a rising age at marriage strongly depresses fertility; the family governs household formation and care of the old. Kinship sets inheritance, residence and the value of sons: Dyson and Moore (1983) linked the north Indian system (village exogamy, patrilocality, low female autonomy) to higher fertility and child mortality, and the south Indian system to lower levels. Religious fertility differentials narrow once education and income are controlled.
Social change in India and tribes. Processes such as Sanskritisation and Westernisation (M.N. Srinivas) and modernisation (Yogendra Singh) alter marriage age, family form and fertility. Scheduled Tribes are specified by the President under Article 342. Census 2011 counted about 10.4 crore STs (8.6% of the population), Madhya Pradesh having the most, with an ST sex ratio of 990 against 943 overall; 75 groups are Particularly Vulnerable Tribal Groups (as of 2026-10).
Social-psychological and communication concepts. The KAP-gap is the gap between knowing and approving of family planning and practising it, later formalised as unmet need. Rogers's diffusion of innovations (1962) sorts adopters into innovators (2.5%), early adopters (13.5%), early majority (34%), late majority (34%) and laggards (16%); opinion leaders mediate (Lazarsfeld and Katz's two-step flow). Berlo's SMCR model (source, message, channel, receiver) frames communication; programmes moved from IEC to behaviour change communication (BCC).
Population trends: world and India. World population passed 1 billion around 1804, 2 billion in 1927, 3 billion in 1960, 6 billion in 1999, 7 billion in 2011 and 8 billion in November 2022 (UN estimates). India's census record has four phases: 1901–21 stagnant (1911–21, with the 1918 influenza, is the only decade of negative growth, −0.31%, so 1921 is the "year of the great divide"); 1921–51 steady growth; 1951–81 rapid growth (peak decadal growth 24.80% in 1961–71); and 1981–2011 high growth with definite signs of slowing (17.7% in 2001–11).
Current scenario and profile of India and states. Census 2011 (final) counted 1,210.9 million people, a sex ratio of 943 females per 1,000 males and a density of 382 per sq km. Among states, Uttar Pradesh was the most populous (about 199.8 million), Bihar the densest (1,106 per sq km), Kerala highest in sex ratio (1,084) and Haryana lowest (879). NFHS-5 (2019–21) put the TFR at 2.0, with Bihar highest (3.0); SRS gave an IMR of 28 per 1,000 live births (2020) and an MMR of 97 per 100,000 live births (2018–20); UN estimates show India passing China as the most populous country in 2023 (all as of 2026-10).
Population census. The UN names four essential features: individual enumeration, universality within a defined territory, simultaneity and defined periodicity. India's first census, non-synchronous, was completed in 1872; the first synchronous census was 1881 under W.C. Plowden. Census 2011, the 15th census and the 7th since Independence, ran under the Census Act 1948 in two phases, houselisting (2010) and population enumeration (February 2011), with reference moment 00:00 hours of 1 March 2011: a modified de facto count. Strengths: complete coverage, village-level data. Weaknesses: the ten-year gap, coverage error (checked by a post-enumeration survey) and age misreporting. The next census has reference date 1 March 2027 (1 October 2026 for snow-bound areas), as of 2026-10.
Vital statistics: CRS and SRS. Registration was voluntary under the Births, Deaths and Marriages Registration Act 1886 and became compulsory under the Registration of Births and Deaths Act 1969 (in force from 1970), with events reported within 21 days; a 2023 amendment created digital registers (as of 2026-10). The CRS suffers incomplete registration (rural, infant and home deaths). The Sample Registration System (pilot 1964–65, full scale 1969–70) is a dual record system: a resident part-time enumerator records events continuously, a supervisor runs an independent half-yearly retrospective survey, and the lists are matched, unmatched events being field-verified. It gives reliable national and state CBR, CDR, IMR, TFR and MMR, but no district estimates.
Population surveys. Surveys give detail but carry sampling and recall error. The NSS began in 1950 under P.C. Mahalanobis; the World Fertility Survey (1972–84) was run by the International Statistical Institute; the DHS programme began in 1984 with USAID support. NFHS is India's DHS, with IIPS Mumbai as nodal agency: NFHS-1 1992–93, NFHS-2 1998–99, NFHS-3 2005–06, NFHS-4 2015–16, NFHS-5 2019–21. The RCH surveys became the DLHS (DLHS-1 1998–99 to DLHS-4 2012–13). The Comprehensive National Nutrition Survey (2016–18) measured micronutrients in those aged 0–19; the Longitudinal Ageing Study in India (wave 1, 2017–18) covers people aged 45 and above and their spouses.
Data appraisal. Errors are of coverage (omission, double counting) or content (misreporting). Whipple's Index: persons reporting ages 25, 30 … 60, divided by one-fifth of all persons aged 23–62, × 100. It is 100 with no preference, 500 if every age ends in 0 or 5, and 0 if those digits are avoided; UN grades: below 105 highly accurate, 105–110 fairly accurate, 110–125 approximate, 125–175 rough, 175 or more very rough. It assumes a rectangular age distribution. Myers' blended index blends counts to offset the fall in numbers with age and scores every digit 0–9: half the sum of absolute deviations from 10%, from 0 to 90. The UN Age–Sex Accuracy Index (joint score) is 3 × the sex-ratio score + the male and female age-ratio scores: below 20 accurate, 20–40 inaccurate, above 40 highly inaccurate. Smoothing uses grouping, moving averages, the UN formula (1/16)(−P(x−10) + 4P(x−5) + 10P(x) + 4P(x+5) − P(x+10)), and Carrier–Farrag, Karup–King–Newton and Sprague.
Worked example
Estimating true births with the Chandrasekaran–Deming formula. In an SRS unit, the enumerator's register lists N1 = 180 births in a half-year, the half-yearly survey lists N2 = 170, and matching finds M = 160 in both.
| Item | Symbol | Births |
|---|---|---|
| Recorded by both | M | 160 |
| Only by enumerator | U1 = N1 − M | 20 |
| Only by survey | U2 = N2 − M | 10 |
| Missed by both (estimated) | U1 × U2 / M | 1.25 |
- Component form: N = M + U1 + U2 + (U1 × U2)/M = 160 + 20 + 10 + 200/160 = 190 + 1.25 = 191.25.
- Product form, as a check: N = N1 × N2 / M = 180 × 170 / 160 = 30,600 / 160 = 191.25.
- Logic: the survey caught 8/9 of the enumerator's births (160/180); under independence its 10 extra births are 8/9 of all the enumerator missed (10 × 9/8 = 11.25), so 1.25 were missed by both.
- Completeness: enumerator 180/191.25 = 94.1%; survey 170/191.25 = 88.9%; combined 190/191.25 = 99.3%.
Common traps
- Reading a Whipple value of 0 as perfect: 100 means no preference; 0 means ages ending in 0 and 5 were avoided.
- Confusing the first census (1872, non-synchronous) with the first synchronous one (1881); 2011 was the 15th overall, 7th since Independence.
- Forgetting the Chandrasekaran–Deming independence assumption: if events missed by one system tend to be missed by the other, the formula underestimates the total.
- Calling the SRS a one-off survey: it is a continuous dual record system giving state, not district, estimates.
- Mixing up the surveys: NFHS is India's DHS (IIPS, MoHFW); the WFS preceded the DHS.
Speed technique
- Whipple shortcut: share of the 23–62 population at ages ending in 0 or 5, × 500.
- Chandrasekaran–Deming in one line: N = N1 × N2 / M.
- UN joint score: 3 × sex-ratio score + both age-ratio scores; cut-offs 20 and 40.
- Census anchors: 1872 first, 1881 synchronous, 1921 great divide, 1951 first after Independence, 2011 the 15th.
Check yourself
- Among persons aged 23–62, 30% report ages ending in 0 or 5. What is Whipple's Index and its UN grade?
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150, rough — 0.30 × 500 = 150, inside the 125–175 band. - Which was India's first synchronous census, and who was Census Commissioner?
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1881, W.C. Plowden — the 1872 count was non-synchronous. - An enumerator records 90 deaths, the survey 80, and 72 match. What is the Chandrasekaran–Deming estimate?
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100 deaths — 90 × 80 / 72 = 7,200 / 72 = 100. - What is the maximum value of Myers' blended index?
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90 — all ages end in one digit: deviations 90 + 9 × 10 = 180, halved. - Which decade recorded negative population growth in India?
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1911–21 — growth of −0.31%, making 1921 the year of the great divide.
Try it: Introduction and Sources of Population Data questions
Real questions from the NET Population Studies bank on exactly this skill. Pick an answer to see the full solution — the intuition, the worked steps, the faster methods and the traps.
Consider the following two statements: Statement I: The decade 1911–21 is the only one in India's census record with negative population growth, which is why 1921 is called the year of the great divide. Statement II: India's decadal population growth in 2001–11 was about 17.7 per cent. In the light of the above statements, choose the correct answer from the options.
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Answer: option A
Statement I: epidemics, notably the 1918 influenza, made 1911–21 the only decade of negative growth (−0.31%), and steady growth followed after 1921, giving it the name 'year of the great divide'; Statement I is true.
Statement II: Census 2011 recorded decadal growth of about 17.7% for 2001–11, down from earlier decades, a definite sign of slowing; Statement II is true.
So Statement I, "The decade 1911–21 is the only one…", and Statement II are both true, option A.
A district had 50,000 people at the start of a year. During the year there were 1,800 births, 700 deaths, 400 in-migrants and 900 out-migrants. Using the balancing equation, the population at the end of the year is:
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Answer: option B
The balancing equation is Pt = P0 + B − D + I − E, where B − D is natural increase and I − E is net migration.
Natural increase = 1,800 − 700 = 1,100 and net migration = 400 − 900 = −500, so Pt = 50,000 + 1,100 − 500 = 50,600; adding and subtracting each component in turn gives the same 50,600.
So the end-year population is 50,600, option B.
In the Sample Registration System, the continuous register kept by a resident part-time enumerator is matched against:
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Answer: option C
The SRS is a dual record system: a resident part-time enumerator records births and deaths continuously, and a supervisor independently conducts a half-yearly retrospective survey of the same units.
The two lists are matched, and unmatched events are verified in the field, which is what makes SRS estimates of CBR, CDR, IMR and TFR reliable at national and state level.
So the second, independent source in the SRS is the supervisor's half-yearly survey, option C.
Match the surveys in List – I with their features in List – II and choose the correct answer from the options. List – I (Survey) | List – II (Feature) --- | --- (a) National Sample Survey | (i) IIPS, Mumbai, as nodal agency (b) World Fertility Survey | (ii) Began in 1950 under P.C. Mahalanobis (c) Demographic and Health Surveys | (iii) Run by the International Statistical Institute, 1972–84 (d) National Family Health Survey | (iv) Programme begun in 1984 with USAID support
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Answer: option B
The National Sample Survey began in 1950 under P.C. Mahalanobis (a – ii), and the World Fertility Survey was run by the International Statistical Institute from 1972 to 1984 (b – iii).
The Demographic and Health Surveys programme followed in 1984 with USAID support (c – iv), and India's own DHS, the National Family Health Survey, has IIPS, Mumbai, as its nodal agency (d – i).
So matching List I, from "National Sample Survey", gives a – ii, b – iii, c – iv, d – i, option B.
Consider the following two statements: Statement I: The Births, Deaths and Marriages Registration Act, 1886 made registration of births and deaths compulsory throughout British India. Statement II: Under the Registration of Births and Deaths Act, 1969, births and deaths are to be reported within 21 days of their occurrence. In the light of the above statements, choose the correct answer from the options.
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Answer: option D
Statement I: the 1886 Act provided only for voluntary registration; registration became compulsory across India only with the Registration of Births and Deaths Act, 1969, in force from 1970. Statement I is false.
Statement II: the 1969 Act requires births and deaths to be reported within 21 days; Statement II is true.
So Statement I, "The Births, Deaths and Marriages Registration Act, 1886…", is false and Statement II is true, option D.
Answer above — every one shows its working.