Perceived or non perceived housing shortage, I believe that people who generally want to live in the city especially apartments do so for convenience e.g. uni, services, and most importantly distance to work (jobs).
A higher AUD, re-tinkering of NRAS starts to take the occupancy rates off units for foreign students. A softer jobs market and demand for workers in metropolitan areas does the same.
Looking at Sydney and Melbourne, I'm not to sure who would really want to live in the city otherwise. However Perth has it's merits but maybe that's more so down to personal preferences.
