LESSON 1.1 — Demography — Concepts, Data Sources & Composition

A. Standard Map

Topic	Governing Source	Exam Focus
Demography — definition	Scientific study of human populations	Distinguish demography from sociology, statistics, population geography
Sources of population data in India	Census of India (decennial), Sample Registration System (SRS), National Family Health Survey (NFHS), Civil Registration System (CRS), UIDAI, PLFS	Which source answers which question; frequency; limitations
Demographic transition	Notion of 4–5 stages; birth rate × death rate → natural increase	Stage identification; drivers of transition
Demographic composition	Age-sex structure, dependency ratio, sex ratio, literacy, worker participation	Definitions + formulae + India/Telangana values
Demographic dividend	Window when working-age share rises	Definition; India’s window; policy implications
Migration	Push/pull factors; Ravenstein’s laws; internal vs international	Types of migration; data sources (Census D-series)

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B. Why It’s Used

TGPSC Paper II §1 opens with demography because every planning calculation — housing demand, school seats, hospital beds, water demand, transit capacity — starts with how many people, of what ages, where, growing how fast. A planner who cannot reason about demographic composition cannot size infrastructure. The exam tests three things here: (a) source awareness — which data source to cite for which claim, (b) conceptual clarity — distinguish natural increase from net migration, dependency ratio from worker participation, and (c) numerical reasoning — compute growth rates, doubling times, and ratios. This lesson builds the foundation; Lesson 1.2 applies it to urbanization trends.

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C. Mechanism in Words

1. Demography is the statistical study of human populations, focused on size, structure, distribution, and change. “Size” = how many people. “Structure” = composition by age, sex, caste, education, occupation. “Distribution” = where they live (spatial). “Change” = how the population is growing or shrinking through three processes: fertility (births), mortality (deaths), and migration (movement). Together these are called the demographic equation: Population(t+1) = Population(t) + Births − Deaths + In-migrants − Out-migrants.

2. India’s population data comes from five complementary sources, each with a different purpose and frequency. The Census of India is the gold standard — a complete enumeration conducted every 10 years (latest 2011; the 2021 Census was deferred and is pending at time of writing). Census gives stock data: how many people, by age, sex, religion, education, occupation, at a moment in time. The Sample Registration System (SRS) fills the gap between censuses by providing annual vital rates — birth rate, death rate, infant mortality rate — through a dual-record system (continuous enumeration + half-yearly retrospective survey). SRS is the only source of reliable infant mortality and natural-increase data in India.

3. The National Family Health Survey (NFHS) is a periodic sample survey (NFHS-5 was 2019–21) focused on health, nutrition, and reproductive indicators — fertility intentions, contraceptive use, anaemia, child stunting. NFHS gives depth on health that Census cannot, but at sample-survey precision, not census-grade totals. The Civil Registration System (CRS) records births and deaths at the office of the local registrar — legally mandatory under the Registration of Births and Deaths Act 1969 — but coverage in India is incomplete outside major cities, so CRS is used for legal documentation more than for statistical totals. The Periodic Labour Force Survey (PLFS) by NSSO gives annual estimates of workforce participation and unemployment — critical for the “worker composition” side of demography.

4. Demographic transition describes the shift from high-birth/high-death to low-birth/low-death as a society modernises. Stage 1 (pre-modern): both rates high, population roughly stable. Stage 2 (early transition): death rate falls fast (public health, sanitation, food security), birth rate remains high → population explodes. Stage 3 (late transition): birth rate begins to fall (education, women’s workforce participation, contraception, urbanisation) → growth slows. Stage 4 (post-transition): both rates low, population stable again, often aging. Some demographers add Stage 5: birth rate below replacement, population shrinking (Japan, Germany, parts of Southern Europe). India is in Stage 3, transitioning toward Stage 4 — total fertility rate (TFR) was 2.0 in NFHS-5 (2019–21), just below the replacement level of 2.1.

5. The demographic dividend is the economic window opened by the transition. When a country’s working-age share (15–64) rises relative to its dependents (children + elderly), and if it can create jobs for those workers, it gets a one-time growth bonus. India’s dependency ratio peaked in the 1990s and has been falling since; the dividend window is open roughly from 2005–06 to 2055–56. A demographic dividend is not automatic — without jobs, education, and women’s workforce participation, the same bulge becomes a disaster (unemployment, social unrest). Planners care because this window shapes housing, education, employment-land, and women’s safety investments for the next 30 years.

6. Migration is the demographic component planners see most directly. Internal migration (within India) is dominated by marriage (about two-thirds of all internal moves, mostly women moving to husband’s residence) and employment (rural-to-urban, especially to metros). The Census classifies migrants by last residence and records streams: rural-to-rural, rural-to-urban, urban-to-urban, urban-to-rural. The D-series tables in the Census are the canonical source for migration statistics. Ravenstein’s “laws of migration” (1885, still surprisingly accurate) state: most migration is short-distance; migration occurs in steps; every migration stream has a counter-stream; urban residents migrate less than rural; females migrate more than males (in India, due to marriage); technology and commerce increase migration.

7. Composition is what makes demography useful for planning. A town of 100,000 people with 35% under age 15 needs very different infrastructure (schools, paediatric care, playgrounds) from a town of 100,000 with 25% over age 60 (geriatric care, accessibility, pension services). The age-sex pyramid visualises this composition. India’s pyramid is transitioning from a true pyramid (broad base, narrow top — young population) to a “beehive” shape (more even distribution — aging population). Telangana is slightly further along this curve than the all-India average due to faster fertility decline in the south.

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D. Core Concept Explanations

C1. Key demographic rates — definitions and India values

Rate	Definition	India (recent)	Telangana
Crude Birth Rate (CBR)	Live births per 1,000 population per year	~13.0 (SRS 2020)	~14.6 (SRS 2020,Sample)
Crude Death Rate (CDR)	Deaths per 1,000 population per year	~6.0 (SRS 2020)	~6.2
Natural Increase Rate	CBR − CDR (per 1,000)	~7.0 per 1,000 (0.7%)	~8.4
Total Fertility Rate (TFR)	Average births per woman over her lifetime	2.0 (NFHS-5, 2019–21)	1.8 (NFHS-5) — below replacement
Infant Mortality Rate (IMR)	Deaths under age 1 per 1,000 live births	~26 (SRS 2020)	~27
Sex Ratio	Females per 1,000 males	943 (Census 2011); 1020 (NFHS-5 sample)	988 (Census 2011)
Child Sex Ratio (0–6)	Girls per 1,000 boys aged 0–6	918 (Census 2011)	945
Life Expectancy at Birth	Years a newborn is expected to live	~70 (M 68.4, F 71.4)	~70.5
Replacement-level Fertility	TFR needed for population stability	2.1	2.1

C2. The demographic equation — worked

A city had 1,000,000 people at start of year. During the year: 18,000 births, 7,000 deaths, 25,000 in-migrants, 5,000 out-migrants.

• Natural increase = 18,000 − 7,000 = +11,000
• Net migration = 25,000 − 5,000 = +20,000
• Total change = 11,000 + 20,000 = +31,000
• End-of-year population = 1,031,000
• Annual growth rate = 31,000 / 1,000,000 = 3.1%

Note that migration contributed nearly two-thirds of the growth — typical of Indian metros. This is the demographic reality that makes urban planning a migration-management problem more than a birth-control problem.

C3. Dependency ratio

The age-dependency ratio is the ratio of persons under 15 plus persons over 64, to persons aged 15–64 (the working-age population), usually expressed per 100.

• Formula: Dependency Ratio = (Pop 0–14 + Pop 65+) / Pop 15–64 × 100
• India (Census 2011): roughly (30.8 + 5.5) / 63.7 × 100 ≈ 57
• Meaning: 100 working-age people support ~57 dependents.
• Trend: falling steadily — the demographic dividend is this ratio going down.

C4. Doubling time — the Rule of 70

A population growing at r % per year doubles in roughly 70 / r years.

• At 2% per year: doubles in ~35 years.
• At 1% per year: doubles in ~70 years.
• At 0.5% per year: doubles in ~140 years.

India’s current natural-growth rate is ~0.7% — doubling time ~100 years if rates held. But state-level variation is large: Bihar at ~1.5% doubles in ~47 years; Kerala at ~0.3% doubles in ~233 years.

C5. Data sources — which one answers which question

Question	Best source	Why
Total population of Hyderabad in 2011	Census 2011	Complete enumeration
Birth rate of Telangana in 2020	SRS 2020	Annual vital rates; Census is decennial
Contraceptive prevalence in India	NFHS-5	Health behaviour surveys need depth, not totals
Number of migrants from AP to Telangana	Census 2011, D-series tables	Migration is a Census question
Workforce participation rate	PLFS (NSSO)	Annual labour data, more current than Census
Live birth legally registered in 2024	CRS	Legal record
Sex ratio at birth	SRS (statistical) or CRS (legal)	SRS preferred for reliability

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E. Worked Numericals and Parameter Tables

E1. Crude rates — full calculation

A district with 500,000 population records 8,500 live births and 3,200 deaths in a year.

• CBR = (8,500 / 500,000) × 1,000 = 17.0 per 1,000
• CDR = (3,200 / 500,000) × 1,000 = 6.4 per 1,000
• Natural increase rate = 17.0 − 6.4 = 10.6 per 1,000 = 1.06%

E2. Infant Mortality Rate

In the same district: 8,500 live births; 245 infant deaths (under age 1).

• IMR = (245 / 8,500) × 1,000 = 28.8 per 1,000 live births

E3. Sex ratio and child sex ratio

A town of 100,000 has 52,000 males and 48,000 females. Children aged 0–6: 6,000 boys and 5,400 girls.

• Sex ratio = (48,000 / 52,000) × 1,000 = 923 females per 1,000 males
• Child sex ratio = (5,400 / 6,000) × 1,000 = 900 girls per 1,000 boys
• The child sex ratio being lower than the overall sex ratio is a flag for sex-selective practices — a classic planning/health-policy signal.

E4. Migration rate

A city of 2,000,000 records 80,000 in-migrants and 30,000 out-migrants in a year.

• Net migration rate = (80,000 − 30,000) / 2,000,000 × 1,000 = 25 per 1,000 = 2.5%
• Gross migration rate = (80,000 + 30,000) / 2,000,000 × 1,000 = 55 per 1,000

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F. Design Criteria

Parameter	Standard / Typical India value	Source
Replacement-level TFR	2.1	UN / demographic convention
Replacement-level CBR (approx)	~21 per 1,000	Depends on age structure
Census periodicity	Every 10 years (mandatory)	Census Act 1948
SRS periodicity	Annual vital rates bulletin	Office of the Registrar General
NFHS periodicity	~every 5–6 years (NFHS-1 1992–93 through NFHS-5 2019–21)	IIPS / MoHFW
Sample size NFHS-5	~636,699 households	NFHS-5 national report
CRS legal basis	Registration of Births and Deaths Act 1969	Mandatory within 21 days of event
Census legal basis	Census Act 1948	Confidential individual data; aggregated release

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G. Application Zones

1. Housing demand estimation — population projection × household size → housing units needed. Demography is step 1 of every Master Plan housing chapter.
2. School and health infrastructure planning — age composition drives primary/secondary/tertiary enrolment demand and paediatric vs geriatric bed requirements.
3. Water and sewerage design — population × per-capita demand (135 LPCD for domestic water per CPHEEO) gives system capacity.
4. Transport planning — workforce participation × trip rate × mode share = transit demand.
5. Telangana-specific: HMDA Master Plan, Hyderabad Metropolitan Development Plan, and the Strategic Road Development Plan all start with population and migration projections for the Hyderabad Metropolitan Region.

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H. Common Confusions

Confusion	Reality
“Sex ratio and child sex ratio are the same thing.”	No — sex ratio is all ages, child sex ratio is 0–6 only. CSR is the leading indicator.
“Natural increase = population growth.”	Only at the national level. At the city level, migration dominates.
“TFR of 2.0 means population is shrinking.”	No — 2.0 is below replacement (2.1) but population momentum (large cohorts entering childbearing age) keeps it growing for ~30 more years.
“NFHS and Census give the same numbers.”	No — NFHS is a sample survey with confidence intervals; Census is complete enumeration. They sometimes disagree by several percentage points.
“SRS is the same as CRS.”	No — SRS is a sample dual-record system for statistics; CRS is the legal registrar of birth/death events.
“Census is annual.”	No — every 10 years. The 2021 Census was deferred; the next enumeration date is pending.
“Dependency ratio is the inverse of workforce participation.”	No — dependency ratio is about age structure; workforce participation is about who actually works. A working-age person can be a non-worker (student, homemaker, unemployed).

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I. Compare & Contrast

I1. CBR vs GFR vs TFR

Measure	What it measures	Numerator	Denominator	Adjustment for age structure
Crude Birth Rate (CBR)	Live births per 1,000 total population	All live births	Total population (all ages, both sexes)	None — “crude”
General Fertility Rate (GFR)	Live births per 1,000 women of reproductive age (15–44 or 15–49)	All live births	Women 15–44/49	Partial — restricts denominator to women of childbearing age
Total Fertility Rate (TFR)	Average births a woman would have over her lifetime at current age-specific rates	Sum of age-specific fertility rates × 5	Synthetic cohort	Yes — fully age-standardised

TFR is the most comparable across populations because it removes age-structure effects. CBR can mislead — a country with many women of reproductive age can have a high CBR but a low TFR.

I2. Census vs SRS vs NFHS

Dimension	Census	SRS	NFHS
Type	Complete enumeration	Sample (dual-record)	Sample survey
Frequency	Decennial	Annual	~5–6 yearly
Coverage	All individuals	~8,000 sample units	~636,000 households (NFHS-5)
Strengths	Total counts; spatial detail	Reliable vital rates between censuses	Depth on health, fertility, nutrition
Weaknesses	Decennial — gets stale	Limited spatial detail below state	Sample errors; not for small-area totals
Best for	Stock data; small areas	Vital rates trends	Health behaviour, policy indicators

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J. Memory Hooks

• “BDM” — Births, Deaths, Migration. The three demographic processes.
• “CSN-CR” (read: “Census-S-N, C-R”) — Census, SRS, NFHS, CRS. The four Indian sources. (Add PLFS for labour.)
• “2.1 = replacement” — below 2.1 = long-term decline; above = growth. India is now at 2.0.
• “70/r = doubling” — quick mental math for any growth rate.
• “Migration = D-series” — when the exam mentions migration, look for the D-series Census tables.
• “Stage 3 India, Stage 5 Japan” — anchor for demographic transition questions.
• “CSN: Census is Stock; SRS is Statistics; NFHS is Narratives” — stock (totals), statistics (rates), narratives (behaviours).

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K. Revision Ladder

Order	Item	Time
1	Memorise definitions: CBR, CDR, TFR, IMR, sex ratio, dependency ratio	30 min
2	Memorise the four data sources + PLFS, their frequencies, and what each is best for	30 min
3	Memorise India-level values for each rate (Census 2011, SRS 2020, NFHS-5)	45 min
4	Practise the worked numericals (CBR/CDR/IMR/sex ratio/doubling time) until automatic	60 min
5	Draw the demographic transition curve (5 stages) and place India on it	20 min
6	Memorise Ravenstein’s laws of migration	20 min
7	Map Telangana values against India values for each rate	30 min

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L. Exam Traps

Trap	Correct response
Question gives CBR and CDR and asks for “growth rate.”	Compute natural increase = CBR − CDR, then convert per-1,000 to per cent. If the question is about a city, flag that migration is missing.
Question asks for “TFR of India” with options 1.6, 1.8, 2.0, 2.4.	2.0 per NFHS-5 (2019–21).
Question states “dependency ratio is rising” for India.	False — it has been falling since the 1990s; the dividend window is open.
Question confuses sex ratio (>6 years / all-ages) with child sex ratio (0–6).	Read the age qualifier in the question carefully.
Question on which source gives “the” infant mortality rate.	SRS — not Census (which gives under-5 mortality as part of a question, not the rate), not NFHS (which gives neonatal / post-neonatal splits).
Question asks if a TFR of 2.0 means population decline.	No — population momentum keeps growth positive for ~30 years after TFR crosses 2.1.
Question asks the periodicity of the Census.	Every 10 years (decennial), per Census Act 1948.

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M. Answer-Writing Cues

• Always state the source and year when quoting a number: “Per SRS 2020, India’s CBR was 13.0 per 1,000.” Unattributed numbers are the most common reason for losing easy marks.
• Show the formula and units in numerical answers. CBR = (Births / Population) × 1,000 = (8,500 / 500,000) × 1,000 = 17.0 per 1,000.
• When asked to “discuss” or “explain,” structure your answer with: definition → formula/source → India value → Telangana value (if relevant) → planning implication. Five moves, full marks.
• When discussing migration, classify by direction (rural-rural, rural-urban, etc.) and reason (marriage, work, education) — not just total numbers.

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N. PYQ Integration

TGPSC Town Planning Assistant prior papers are not consistently public. Pattern questions based on the exam’s expected structure:

Pattern question 1 — Source identification

Q. The most reliable source of annual birth and death rates in India is:
– (A) Census of India
– (B) Sample Registration System (SRS) ✓
– (C) National Family Health Survey (NFHS)
– (D) Civil Registration System (CRS)

Ans: (B). SRS provides annual vital rates using a dual-record system designed for statistical reliability. Census is decennial; NFHS is periodic; CRS has coverage gaps.

Pattern question 2 — TFR interpretation

Q. A Total Fertility Rate of 2.0 in India (NFHS-5, 2019–21) implies:
– (A) Population is shrinking
– (B) Population is at replacement level
– (C) Population is below replacement level but still growing due to momentum ✓
– (D) Population has stabilised

Ans: (C). Replacement level is TFR 2.1. At 2.0, India is below replacement, but population momentum (large cohorts entering reproductive age) keeps growth positive for ~30 years.

Pattern question 3 — Numerical

A town of 200,000 population records 4,000 births and 1,500 deaths in a year. The natural increase rate is:
– (A) 7.5 per 1,000
– (B) 12.5 per 1,000 ✓
– (C) 15.0 per 1,000
– (D) 25.0 per 1,000

Ans: (B). CBR = 4,000/200,000 × 1,000 = 20.0. CDR = 1,500/200,000 × 1,000 = 7.5. Natural increase = 20.0 − 7.5 = 12.5 per 1,000.

Pattern question 4 — MSQ-style

Q. Which of the following are recorded in the Census of India D-series tables?
– (A) Births by age of mother
– (B) Migrants by last residence ✓
– (C) Migration streams (rural-urban etc.) ✓
– (D) Reason for migration ✓

Ans: (B), (C), (D). The D-series covers migration. Births by age of mother are in the SRS / NFHS, not the Census.

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O. Mini-Check — Lesson 1.1

1. Define demography in one sentence.
2. Write the demographic equation.
3. Name the four major Indian sources of population data and the frequency of each.
4. Define CBR. Compute CBR for a population of 100,000 with 1,800 births.
5. Define TFR. What is India’s TFR per NFHS-5? Is it above or below replacement?
6. What is the difference between sex ratio and child sex ratio?
7. Define dependency ratio. Is India’s dependency ratio rising or falling?
8. State the Rule of 70 and apply it to a 2% growth rate.
9. List Ravenstein’s laws of migration (any four).
10. Which data source gives the most reliable Infant Mortality Rate for India?

Answers:
1. Demography is the statistical study of human populations, focused on size, structure, distribution, and change through fertility, mortality, and migration.
2. Population(t+1) = Population(t) + Births − Deaths + In-migrants − Out-migrants.
3. Census (decennial), SRS (annual), NFHS (~every 5–6 years), CRS (continuous, legally mandatory). Add PLFS for labour data (annual).
4. CBR = (live births / total population) × 1,000 = (1,800 / 100,000) × 1,000 = 18.0 per 1,000.
5. TFR = average births per woman over her lifetime at current age-specific rates. India TFR = 2.0 (NFHS-5, 2019–21) — below replacement (2.1).
6. Sex ratio = females per 1,000 males (all ages). Child sex ratio = girls per 1,000 boys aged 0–6. CSR is the leading indicator.
7. Dependency ratio = (Pop 0–14 + Pop 65+) / Pop 15–64 × 100. India’s is falling since the 1990s — the demographic dividend window.
8. Doubling time ≈ 70 / growth rate %. At 2%, doubling time ≈ 35 years.
9. Most migration is short-distance; migration occurs in steps; every stream has a counter-stream; urban residents migrate less than rural; females migrate more than males (in India); technology and commerce increase migration. (Any four.)
10. The Sample Registration System (SRS) — dual-record system, designed for vital-rate reliability.

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