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landslide, earthquakes, volcanic eruption,cyclones, tsunami, etc., increase of pollution,
desertification, lack of drinking water, etc.
We can measure migration by four different ways which are explained below:
a. In-Migration Rate(In- MR)
b. Out - Migration Rate (Out MR)

c. Net Migration Rate (NMR)
d. Gross Migration Rate (GMR)

a. In-Migration Rate(In- MR)
The total number of in-migrants in 1000 mid year population in a place in a certain year
is called as in-migration rate.
Mathematically,
Total number of in migrants in a place in a year
In-MR = × 1000
Mid year population of that place in the year
It is also expressed per 1000.

Worked out example: 9

The population of a city in 2008 A.D. was 225000. In the same year, there were 38000 in-
migrants in the city, calculate the in-migration rate of that city in that year.

Solution:
Given,
In a city in 2008 A.D.,
Number of in-migrants = 38000
Total population = 225000
In - migration Rate (InMR) = ?
We know,

Total number of in migrants in a place in a year
In-MR = × 1000
Mid year population of that place in the year

38000
= × 1000
225000
= 168.88
In-MR of that city in 2008 A.D. was 168. 88 per 1000.

In the above example, In-MR is calculated as 168.88 per 1000. It means that nearly 169
people in-migrated among 1000 mid year population in a city in 2008 A.D.

GREEN Health, Population and Environment Education Book-10 25