From a demographic point of view, two components shape the change in population size: the balance of births and deaths and the migration balance (balance of inflows and outflows). On sub-national level (e.g. federal states, political districts, municipalities), the total migration balance is the sum of the and the .
Due to occasional inconsistencies and singular adjustments in the administrative data of the Central Population Register and the Central Civil Status Register on which population statistics are based, not all changes in population status can be attributed to either the balance of births and deaths or the migration balance. This residuum of the population change is marked in the tables as "statistical adjustment".