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