Immigration rates and emigration rates are calculated in the same manor as birth and death rates
The difference between the two gives the net migration rate
Birth rate - Death Rate +/- Net Migration rate = Population growth rate
One way to show these stats is the demographic transition model
Summary
Immigration and emigration is also one of the factors of certain countries populations are raising and falling. Many people immigrate because they are trying to escape poverty or low living standards in the country they are in. The difference between immigration and emigration gives the net migration rate, and then by subtracting the death rate from the birth rate and then adding or subtracting the Net migration rate you are given the population growth rate. A way to show this is by using demographic transition models which show the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system.