Birth + immigration - death - emigration

In general birth and death and/or immigration and emigration processes will be included therefore the need not to be constant with time. 

Finally birth and death processes and/or immigration and emigration processes are considered. The individual probabilities per time unit for birth (immigration) and death (emigration) of g members of 9a with attitude i are denoted by... 

Increase in population = births — deaths + immigration — emigration... 

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