Decades of housing policy failure - here's a solution - Squatting!, page-50

There would a significant number or retirees living in 3-5 bedroom homes that have excess rooms that are never used that would be better utilised by young families.

Try attempting to get these people to sell & move into 2 bedroom apartments or retirement villages, political suicide!
The whole tax/benefit system is geared up to allow them to stay in their homes ie houses aren't included in asset tests.

The answer is simple supply & demand must be brought back to balance. Significantly reduce demand & significantly increase supply.
At the moment we have the worst both worlds, demand is too high & supply is too low.