What is Demography? Complete Guide for Beginner

What is Demography?

Demography (Population Study) is the scientific study of human population, concerned with population size, composition, distribution and changes due to fertility, mortality and migration. 

The chart below illustrates a visual example of demography, showing Pakistan’s population growth from 1951 to 2023:

Vital Events

Vital events are major events of human life that affect the size, composition and distribution of a population. 
Examples: Births, deaths, divorces, marriages, migrations etc.

Vital Statistics

The numerical records of vital events in a population. 
Example: 2000 died in this year and 3000 born etc.

Key Aspects of Population Studies

• Population Size

  The total number of individuals living in a specific area.
  Example: A city has a population size of 2.5 million. Here, 2.5 million is the population size of that city. 

• Population Composition

  The characteristics of the population such as age, sex, ethnicity, religion, education, occupation and socioeconomic factors. 
  Example: 30% of the population is under age 18. 

• Population Distribution

  The geographical pattern of where people live. 
  Example: 70% of population lives in urban areas and 30% lives rural areas.  

Key Processes of Population Studies

• Fertility

  The birth rate in a population and its impact on population growth. 
  Example: If 20 babies are born in a village this year, the village population increases by 20. 

• Mortality

  The death rate in a population and its impact on population size and life expectancy. 
  Example: If 20 people die in a village this year, the village population decreases by 20.

• Migration

  The movement of people within or between countries, which changes size, composition and distribution of population. 
  Example: If 20 people move from Village A to Village B, Village A’s population decreases and Village B’s population increases by 20.  

Sex Ratio

Sex Ratio (or Gender Ratio) is the number of males per 100 females in population.

Formula:

Interpretation:

• Sex Ratio > 100 → more males than females.
• Sex Ratio < 100 → more females than males.
• Sex Ratio = 100 → equal number of males and females.

Example: 
In a district, there are 120,000 males and 100,000 females.

Sex Ratio = 120, which means there are 120 males for every 100 females in that district. 

Child-Women Ratio (CWR)

Child-Women Ratio measure the number of children aged 0-4 years per 1000 women of childbearing age (usually 15 to 49 years) in population.
Formula: 

Interpretation: 

• Higher CWR → generally indicates higher fertility.
• Lower CWR → generally indicates lower fertility.

Example:

In a village, the number of children aged 0-4 years are 200 and number of women aged 15-49 are 500. 

CWR = 200, which means there are 100 children (0-4 years old) per 1,000 women of childbearing age (15-49 years old).

 

 

Crude Birth Rate (CBR)

Crude Birth Rate is the number of live birth per 1,000 people in a population in a given year. 
Formula: 

Example: 
A village with a population of 1,000 at the start of 2024, increasing to 1,200 at the end of the year, if one baby is born each month.

CBR = 10.91, which means approximately 11 babies are born for every 1,000 people in the village in 2024.

Age Specific Fertility Rate (ASFR)

Age Specific Fertility Rate measure the number of live births per 1,000 women of a specific age group (usually 5 year interval). 
Formula: 

Example: 
In the age group 20-24, there are 200 live births and the number of women aged 20-24 (mid-year) is 5,000.

Women aged 20-24 are giving 40 births per 1000 women in that age group. 

General Fertility Rate (GFR)

General Fertility Rate measures the number of live births per 1,000 women of childbearing age (15-49 years) in a given year. 
Formula:

Example: 
In a year, total live births are 1,000 and the mid year population of women (15-49) is 20,000.

Women of childbearing age (15-49) are reproducing 50 births per 1000 women in a year.