Page 28 - Health, Population and Environment Education 10

Note
While calculating NMR, if the value of NMR is positive, it shows that there is more
number of in-migrants than out migrants in a place which ultimately increases
population in a place.
If the value of NMR is negative, it shows that there is more number of out migrants than
in-migrants in a place which ultimately decreases the population in that place.

d. Gross Migration Rate(GMR)
The sum of in-migrants and out-migrants in a place in a year is called as gross migration
rate.

Mathematically,
Number of in-migrants + Number of out migrants
GMR = × 1000
Mid year population of a place in the year

It is also expressed per 1000.
Activity: 3

The mid year population of a town is 25,455. If 590 people came from the village and 466
left the town, what will be the gross migration rate in that town?

Other Measurements

a. Rate of Natural Increase(RNI)
The difference between CBR and CDR is called as rate of natural increase.
Mathematically,
CBR – CDR
RNI = × 100
1000
It is expressed in percentage. In RNI, there is no discussion of migration, only data on
birth and death are used.

Worked out example: 12
If CBR and CDR of a country are 32. 7 per 1000 and 9.2 per 1000 respectivley, what will be
the rate of natural increase?

Solution:
Given,
In a country
CBR = 32.7

28 GREEN Health, Population and Environment Education Book-10