 ## Some Important Measures of Population Change

Subject: EPH #### Overview

Population Doubling Time is the estimated time taken to double the population. This is the note about the measures of population change.

#### Rate of Natural Increase (RNI)

If the population is increased due to the difference of birth rate and death rate, it is called rate of natural increase (RNI). In other words, it is the difference between crude birth rate and crude death rate.

If the birth exceeds the death (+ve RNI), the population increases and vice versa. Similarly, if the birth equals to the death, then population becomes stable (or zero rate of natural increase).

#### Population Growth Rate The population of a country changes continuously. Birth, death and migration are the demographic elements behind the population change. Population growth rate shows either the population of a country increasing or decreasing. Population growth is the sum of RNI and net migration, it is expressed in percent.

#### Sex Ratio

Sex ratio is the ratio of males to females in a given population and usually expressed as the number of males per 100 females. It is used for expressing sex composition of thepopulation.

#### Dependency Ratio The dependency ratio is measured by considering the distribution of the population by three broad groups such as 0-14, 15-59, and 60 and above. In these age groups, the age group of 0-14 and 60 above are not productive and may not be able to earn their livelihood so they should depend upon the age groups of 15-59 years. Dependency ratio shows the number of persons dependent upon every 100 people of independent groups.

#### Population Doubling Time

Population Doubling Time is the estimated time taken to double the population. The doubling time is calculated by a simple mathematical calculation. Accordingly, if a number is increased by 1 percent, in approximately 70 years, it will be doubled. If a population is growing at 1 percent per year, it takes about 70 years to double.

##### Things to remember
• If the population is increased due to the difference of birth rate and death rate, it is called rate of natural increase.
• Population growth is the sum of RNI and net migration.
• Sex ratio is the ratio of males to females in a given population and usually expressed as the number of males per 100 females.
• Population Doubling Time is the estimated time taken to double the population.
• 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.
##### Videos for Some Important Measures of Population Change
The rate at which the population size of a certain country is increases or decreases over a certain time period, generally one year, is termed as population growth rate. It is expressed in percent.
According to the 2058 census, the annual population growth rate of Nepal was 2.25 %.
When the growth rate is found negative e. g. -0.5 %, it is indicated that the population of a certain country is decreasing.

If the population growth rate of a certain country is 2 %, it will take 35 years (70/2) to double.

We calculate dependency ratio by dividing the total number dependent population (people below 15 years and above 60) by the total number of dependent population (people of 15-59 years of age) and multiplying the quotient by 100.
Dependency ratio =( Dependent population / Independent Population)× 100

We calculate sex ratio by dividing the total number of males by total number females and multiplying the quotient by 100.
Sex ratio = (Male population / Female population)× 100

The difference between sex ratio and dependency ratio is given below:

 Sex ratio Dependency ratio The sex ratio, generally, denotes the number of males per 100 females. The result which comes after dividing the population of 0-14 and 60 years and above by the population of 15-59 years age group and multiplied by 100 is called dependency ratio. Sex ratio =Total number of males × 100 / Total number of females Dependency ratio=Number of dependence × 100 / Active population It is used to find out the ratio of male and female. It is used to find out the ratio of active and dependent population. Sex ratio increases due to preference to son. It increases due to increasing health status and facilities.
Difference between population size and population growth rate is given below:
 Population size Population growth rate Population size means the number of person s in population Population growth rate means the joint sum of natural growth rate of population and the net migration. Population size is measured in number. Population growth rate is measured in percentage.
Here,
Midyear population (P) =4, 00,000
Birth (B) =25,000
Death (D) = 4,500
Immigration (I)=4000
Emigrants (E) =1098
According to the formula,
Net Migration rate(NMR) = ( (I-E) × 1000 ) / P
= ((4000-1098) × 1000) / 4,00,000
= (2092) / 400
= 7.25 Per thousand

Gross migration Rate(GMR) = ((I+E) × 1000 ) / P
= ((4000+1098) × 1000) / 4,00,000
= 5098 / 400
= 12.74
GMR =12.74 per thousand

Rate of Natural Increase:
= ((CBR-CDR) × 100) /1000
First of all let's calculate CBR & CDR
CBR = B × 1000 / P
= 25000 × 1000 / 4,00,000
=250 / 4
= 62.5

CDR= D × 100 / P
= 4500 × 1000 / 400000
= 45 / 4
= 11.25

CBR =62.5 per thousand CDR= 11.25 per thousand
Now,
We know that
RNI =((CBR-CDR) × 100) / 1000
=(62.5-11.25) × 100) / 1000
= -5.12 %
Rate of natural increase -5.12 %

Population Growth Rate
= (CBR-CDR+NMR) × 100 / 1000
= 58.5 / 10
= 5.85 %
Rate of population growth = 5.85 %

Population Doubling times
= 70 / Annual growth rate
=70 / 5.85
= 11.96
Population doubling time = 11.95 %

Given,
Crude Birth rate(CBR)= 20.5
Crude death rate(CDR)= 12.6
Net migration rate (NMR)= 8
Rate of natural increase (RNI)= ?
Population growth rate (PGR)= ?

We know,
RNI = (CBR-CDR)/1000*100
= (20.5-12.6)/1000*100
=. 79

Again PGR = (CBR-NMR)/1000 *100
=20.5-12.6+8/1000*100
=1.59%

Therefore, the RNI for the country's population is. 79% and PGR is 1.59% per annum.