In 1976, 1986 and 1996 house prices were just under 3.7 years wages.. That is the normal cost of a house that globally is classed as affordable. Prices cycle up and down from there but over all house prices track CPI maintaining this normal cost ratio.
At the end of the 90's you had low interest rates, and the gov introduced a 50% discount on CGT and encouraged investing (as they wanted to encourage people not to be on the pension with older population growth forcasted).
this saw everyone taking advantage of low interest rates and tax discount, and borrowing to invest in shares and housing.
so after a constant stead price of housing, it went from 3.7x in 1996 up to 7x in 2003
Thats why people have called Australian housing as being in a bubble since 2003 as its almost double the all time norm.
