Notes on demography from arpit psm

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I now have comprehensive coverage of the demography chapter from Park's PSM. Let me compile the complete structured notes:

Demography - Notes from Park's Textbook of Preventive and Social Medicine (PSM)

Chapter motto: "Delay the first, postpone the second and prevent the third"

1. DEFINITION

Demography is the scientific study of human population. It focuses on three observable phenomena:

(a) Changes in population size (growth or decline)
(b) Composition of the population
(c) Distribution of population in space

It deals with five demographic processes:

Fertility
Mortality
Marriage
Migration
Social mobility

These five processes continuously determine size, composition, and distribution of a population.

Main sources of demographic statistics in India:

Population censuses
National Sample Surveys
Registration of vital events
Adhoc demographic studies

2. DEMOGRAPHIC CYCLE (Demographic Transition)

The history of world population since 1650 shows a 5-stage demographic cycle:

Stage	Name	Birth Rate	Death Rate	Population trend	India's status
1st	High Stationary	High	High	Stationary (cancel each other)	India till 1920
2nd	Early Expanding	High/rising	Declining	Growing	S. Asia, Africa currently
3rd	Late Expanding	Falling	Low	Growing (births > deaths)	India currently
4th	Low Stationary	Low	Low	Stationary	UK, Austria, Scandinavian countries
5th	Declining	Very low	Low	Declining	Some European countries

India was in Stage 1 until 1920, and has now entered Stage 3.
Zero population growth recorded in Austria during 1980-85.
Most industrialized countries have undergone demographic transition: High BR + High DR → Low BR + Low DR.

3. POPULATION GROWTH RATES

Formula - Doubling time (Rule of 70): Approximately 70 / growth rate (%) = years to double

Rating	Annual growth rate (%)	Years to double
Stationary population	No growth	-
Slow growth	< 0.5	> 139 years
Moderate growth	0.5 - 1.0	139-70 years
Rapid growth	1.0 - 1.5	70-47 years
Very rapid growth	1.5 - 2.0	47-35 years
"Explosive" growth	2.0 - 2.5	35-28 years

Key facts:

World population growth rate was at peak ~1970 (~1.92%) and has since declined to 1.1% in 2019
Africa: ~2.6% | Latin America: ~1.0% | Europe/industrialized: ~0.3% | Asia: ~0.9%
World population: 7.7 billion (2019) → 8.5 billion (2030) → 9.7 billion (2050) → 10.9 billion (2100)
India is projected to surpass China as world's most populous country around 2027
In 2018, for the first time in history, persons ≥65 years outnumbered children <5 years worldwide
Life expectancy at birth reached 72.6 years globally in 2019

4. DEMOGRAPHIC TRENDS IN INDIA

Demographic indicators are divided into:

A. Population Statistics

Population size
Sex ratio
Density
Dependency ratio

B. Vital Statistics

Birth rate
Death rate
Natural growth rate
Life expectancy at birth
Mortality and fertility rates

Key facts about India:

Population (mid-2020): 1,400.2 million - 2nd most populous after China
India has only 2.4% of world's land area but supports 17.5% of world's population
India is 7th in land area but 2nd in population

5. SEX RATIO

Defined as: Number of females per 1000 males
Sex ratio in India (2011 census): 940 females per 1000 males
In 2011, the sex ratio improved by 4 points (from 906 to 940 over the decade... wait - this specific line read: "has been 4 points from 906 to 902 over the decade" which appears to be from the child sex ratio)
Child Sex Ratio (0-6 years): declined from 906 to 902 per 1000 males (2011 census)

6. DENSITY OF POPULATION

Density = Total population / Land area (persons per sq. km)
India's density (2020): 464 persons per sq. km

Historical trend in India:

Year	Density (per sq. km)
1901	77
1921	81
1951	117
1971	177
1981	216
1991	267
2001	325
2011	382
2020	464

7. URBANIZATION

Urban area (India): Towns with municipal corporation/board OR places with:
- ≥5,000 inhabitants
- Density ≥390 persons per sq. km (or ≥1,000 per sq. mile)
- Pronounced urban characteristics
- ≥3/4 of adult male population in non-agricultural work
Urban population of India (2019): 471.828 million (34.5%)
Most populous cities: Mumbai (12.69M) > Delhi (10.93M) > Bengaluru (5.10M) > Kolkata (4.63M) > Chennai (4.33M)
India's population remains predominantly rural with agriculture as main occupation

8. DEPENDENCY RATIO

Total Dependency Ratio Formula:

Total Dependency Ratio = (Population 0-14 yrs + Population ≥65 yrs) / Population 15-64 yrs × 100

Subtypes:

Young age dependency ratio = Population 0-14 years
Old age dependency ratio = Population ≥65 years

India (mid-2020):

Age 0-14 years: 26.2%
Age 15-64 years: 67.3%
Age ≥65 years: 6.6%
Total dependency ratio = (26.2 + 6.6) / 67.3 × 100 = ~48.7%

Key concepts:

Dependency ratio tends to decrease in early development stages (declining fertility reduces child population)
Eventually shifts from child dependency to old age dependency as fertility declines and life expectancy increases
"Demographic bonus" = the period when dependency ratio declines due to declining fertility (before it rises again due to increasing longevity)
Rapid decline in dependency ratio (especially child dependency) is a key factor underlying rapid economic development

9. VITAL STATISTICS / FERTILITY INDICATORS

Key fertility measures (covered in the chapter):

Indicator	Definition
Crude Birth Rate (CBR)	Live births per 1000 mid-year population per year
General Fertility Rate (GFR)	Live births per 1000 women aged 15-49 years per year
Age-Specific Fertility Rate (ASFR)	Live births to women in a specific age group per 1000 women in that age group
Total Fertility Rate (TFR)	Sum of ASFRs for all age groups (15-49) - average number of children a woman would have if she lived through her reproductive years at current age-specific fertility rates
Gross Reproduction Rate (GRR)	Average number of daughters a woman would have; TFR × proportion of female births
Net Reproduction Rate (NRR)	Like GRR but adjusted for mortality; NRR = 1 means exact replacement

Family size (demographic definition): Total number of children a woman has borne at a point in time (completed family size).

10. KEY MORTALITY INDICATORS

Rate	Formula
Crude Death Rate (CDR)	Total deaths per 1000 mid-year population per year
Infant Mortality Rate (IMR)	Deaths in infants <1 year per 1000 live births
Neonatal Mortality Rate	Deaths in first 28 days per 1000 live births
Perinatal Mortality Rate	Stillbirths + neonatal deaths in first 7 days per 1000 total births
Maternal Mortality Rate (MMR)	Maternal deaths per 1000 (or 100,000) live births

11. CENSUS

A census is the official enumeration of the population
India conducts census every 10 years
Provides data on: population size, sex ratio, literacy, age distribution, occupation, etc.
India 2011 Census - population: 1,210 million

12. VITAL STATISTICS REGISTRATION

Registration of vital events: births, deaths, marriages, divorces
Compulsory registration of births and deaths in India under the Registration of Births and Deaths Act, 1969
Completeness of registration is a major problem in developing countries

Quick Revision Summary (High-Yield for Exams)

Fact	Value
Demographic processes	Fertility, Mortality, Marriage, Migration, Social mobility
Demographic cycle stages	5 stages
India's current demographic stage	3rd stage (Late Expanding)
India till 1920	1st stage (High Stationary)
World population peak growth year	~1970 (1.92%)
India's population (mid-2020)	1,400.2 million
India's % of world land area	2.4%
India's % of world population	17.5%
India projected to surpass China	~2027
India's density (2020)	464/sq. km
India's urban population (2019)	34.5%
India's dependency ratio (2020)	~48.7%
Life expectancy at birth globally (2019)	72.6 years
Sex ratio India (2011)	940 females/1000 males
NRR for replacement	= 1

Source: Park's Textbook of Preventive and Social Medicine, Chapter on Demography (Block 7, pp. 566-596)

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