# Types & Measures of Migration

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Types of Migration:Followings are the different types of migration given by the demographers & sociologists.
i. Immigration & Emigration
ii. In-migration & out-migration
iii. Gross Migration & Net Migration
iv. Internal Migration

Immigration & Emigration:
Immigration is coming from one country to another.
Emigration is going from one country to another.
In-migration & out-migration:
In-migration is the migration within a particular area. Out migration is the migration out of a particular area. These two types of migrations are applicable to internal migration.
Internal migration:
Internal migration is the movement of people within the country. Its range is from a few kilometers to several thousand kilometers. In this type of migration, people are changing their residence from one town to another and one village to another due to marriage, occupation etc.
Gross-migration:
Gross migration is the volume of migration. It is the total number of arrivals of immigrants and departure of in-migrants and out migrants.
Net migration is the balance of migration. It is the difference between the total number of persons coming in and leaving out or the difference between immigrants and emigrants.

Basic measures of migration:
Four types of migration rates are commonly used.
i. In-migration rate, I/P i.e I divided by P
ii. Out migration, O/P
iii. The gross migration rate, (I+O)/P
iv. The net migration rate, (I-O)/P
Where, I is the number of in-migrants during a specified time to a given area.
O is the number of out migrants during a specified time from a given area.
P is the population of the given area at either at the beginning, end or the midpoint of the migration interval.
Balancing equation method:
In any given area, the number of net migrants during an interval between two censuses can be estimated by the method of a balancing equation as follows,
Net migration = Pt+n - Pt - nBnDt
Where,
n is the intercensal interval,
Pt+n is the population of the area at time (t+n)
Pt is the population of the area at time t
nBt is the number of births occurring during the interval t to (t+n).
nDt is the number of death occurring during the interval t to (t+n).