Notes, Exercises, Videos, Tests and Things to Remember on Some Important Measures of Population Change
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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).
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 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.
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 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.
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.|
Midyear population (P) =4, 00,000
Birth (B) =25,000
Death (D) = 4,500
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
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
CDR= D × 100 / P
= 4500 × 1000 / 400000
= 45 / 4
CBR =62.5 per thousand CDR= 11.25 per thousand
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
Population doubling time = 11.95 %
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)= ?
RNI = (CBR-CDR)/1000*100
Again PGR = (CBR-NMR)/1000 *100
Therefore, the RNI for the country's population is. 79% and PGR is 1.59% per annum.