Question

How we get the next year population with the current year net reproduction rate?

Answer 1

Population Growth - Basic Information 
    All populations change in size with time 
        - if births exceed deaths, the population grows 
        - if deaths exceed births, the population shrinks 
        - only when births equal deaths does the population stay the same

Other Population Growth Factors 
    Populations can also change size if organisms move in (immigration) or leave (emigration)

Putting It All Together 
    We can write a simple equation to show population growth as:

            Change in Population Size = (Births + Immigration) - (Deaths + Emigration)

Expressing Population Changes as a Percentage 
    Suppose we had a population of 100,000 individuals.  Suppose in one year there were 1000 births, and 500 deaths. 
    What percentage of the population were births? 
                    1000/100,000 = 0.01, or in percentage terms, this is 1% of the population.

    What percentage of the population were deaths? 
                    500/100,000 = 0.005, or in percentage terms, this is 0.5% of the population.

    Assume immigration equals emigration.  If so, then they cancel out of our population equation.   We'll come back to 
this assumption later.

Answer 2

Net reproduction rate or NRR of a country gives the calculation of the number of daughters that would be born to a female if she dies within a specific age of fertility .

This is quite similar to the goes reproduction rate but it takes into an account that few women will die before her childbearing years.

The present year NRR can give an approximate estimation of the coming year population.