## Measures of Population Change

Subject: Social Studies and Population Education

#### Overview

Fertility refers to the reproductive function. It is the ability to bear offspring. It is the production of live birth which starts when a women gives the first birth. This note has information about measures of population change.

##### Measures of Population Change

Demographic measures are the actual changes in size, composition and distribution due to changes in demographic components like birth, death and migration, as a result of their respective processes like rate of fertility, mortality and migration. Demographic measures are enumerated by applying specific formulas for a specific type of measurement.

#### Fertility Rate

Fertility refers to the reproductive function. It is the ability to bear offspring. It is the production of live birth which starts when a woman gives the first birth. Its period is generally 15-49 years of age. Likewise, fecundity is the psychological capacity to participate in reproduction. It starts with the regulation of monthly menstrual cycle. Fertility results in a birth. It is measured by the actual number of births. The measures that are used to estimate fertility rate are as follows: -

##### 1. Crude Birth Rate(CBR)

Crude Birth Rate is the simplest way of measuring fertility. The crude birth rate of an area is defined as the number of live births occurring in that area, in a given period of time, usually a year, divided by the total population of that area as estimated in the middle of the year. The rate is expressed in terms of 'per 1000 of the population'.

##### 2. Age-Specific Fertility Rate(ASFR)

Fertility rates may be computed for each age from 15-49 years. However, computation of each year may not be necessary, generally fertility rates for five-year age groups are measured. Such fertility rates are known as age-specific fertility rate.

##### 3. Total Fertility Rate(TFR)

Total fertility rate is referred to the number of children of women, would bear during her childbearing age under ongoing age-specific fertility rate (ASFR). It is measured as the sum of age-specific fertility rates calculated for the same single year. Since, the ASFR is calculated for 5 year age groups, the sum of ASFR’s need to be multiplied by 5.

##### Things to remember
• Demographic measures are the actual changes in size, composition and distribution due to changes in demographic components like birth, death and migration, as a result of their respective processes like rate of fertility, mortality and migration.
• Fertility refers to the reproductive function. It is the ability to bear offspring. It is the production of live birth which starts when a women gives the first birth. Its period is generally 15-49 years of age.
• The measures that are used to estimate fertility rate are as follows: -  Crude Birth Rate(CBR), Age-Specific Fertility Rate(ASFR),  Total Fertility Rate(TFR)

• It includes every relationship which established among the people.
• There can be more than one community in a society. Community smaller than society.
• It is a network of social relationships which cannot see or touched.
• common interests and common objectives are not necessary for society.
##### Why Do We Have More Boys Than Girls?

Given,
Total live birth =915
Mid-year population =32423
Crude Birth Rate (CBR) =?

We know,
CBR = $\frac {Total\; live\; birth}{Total\; mid-year\; population}$ × 1000
= $\frac {915}{32425}$ × 1000
= 28.22 per thousand

Therefore, the crude birth rate of the district was 28.22 per thousand mid-year populations.

Birth, death and migration are the major three factors of population change.

Fertility refers to the actual birth performance by a woman in her childbearing age i.e. 15-49 years. It determines the growth of population.

Crude Birth Rate (CBR) is calculated by individual the total number of live birth in a year by the mid-year total population of that year and it is multiplied by 1000 to calculated in per thousand population.

Crude Birth Rate(CBR)= $\frac {total\; number\; of\; live\; birth\; in\; a\; year}{mid-year\; total\; population}$× 1000

or, CBR = $\frac BP$ ×1000

Where,

B= Total no. of live birth in a year

P= Mid-year total population

Age-Specific Fertility Rate is the total number of live birth performed by the women of specific age group(for eg. 15-19,20-24,25-29 etc) in a year in per thousand population of their age group.

It is calculated by dividing the number of live births given by the mid-year population of the same age group and multiplied by 1000 to measure in per thousand.

The total number of birth given by a woman during her reproductive period is called total fertility rate. TFR is calculated from Age-specific Fertility Rate(ASFR). Different age-specific fertility rates are summed up and the sum is multiplied by the number of years in the age group. And the product is divided by 1000.

The formula is:

TFR = $\frac {sum\; of\; ASFR}{1000}$× 5

Solution,

Here,

Mid-year female population of age group 25-30 (Ps) = 32600

The total no. of live birth given by the women of 25-30 year age group (Bs) = 480

We know that,

ASFR = $\frac {Bs}{Ps}$× 1000

= $\frac {480}{32600}$ × 1000

= 14.724 per thousand

Therefore, the ASFR of the group of 25-30 in Pokhara city was 14.724 per thousand.