In terms of the migration statistics of the Federal Statistical Office:
external migrations cover movements back and forth across the borders of Germany. External migration also includes persons intending to take up temporary accommodation abroad or in Germany. The registration laws do not cover de-registration in cases where the previous abode is kept on alongside a new address. Only movements across the borders of Germany which are combined with relinquishment of the address in Germany are taken into consideration.
Selected information about External migration:
Further information can be found on the topic or keyword search.