Although each nation and every culture has its own interest points and long-term economic plans for accepting immigrants and refugees, but in general, there are some variables that seems essential, for most: (1). The higher educational level of younger individual, for being active, productive and flexible in the new culture. (2). The higher financial status of younger-group rather than seeking or providing, in the new unfamiliar environment (social safety). (3). General condition of older arrivals, related to their lack of flexibility, productivity & self-maintenance. (4). Health stand of retired immigrants, and their need of a provided healthcare facilities, by governmental institutes. (5). The possible number of supporter-family member, at the time of arrival, to lighten up the load for the national supportive systems.     

This is worth reading http://link.springer.com/article/10.1007/s11948-015-9667-8 

this also might be of interest for you if you are investigating the inner-organisational structures of DIBP ( text is written from a network perspective): http://www.andrew.cmu.edu/user/krack/documents/pubs/2012/2012PolInOrgs.pdf