Population growth, arguably, is one of the main factors which fuel property prices and is even more pronounced in Australia given the majority of the people live in a handful of state capital cities. In fact, and I speak only of Melbourne because I grew up there, it is one of the largest cities by land area in the world and it probably goes the same for Sydney. It would be no surprise to me that Melbourne, Sydney (and Brisbane one day) become one of the most densely populated cities in the World. Hence, property prices will continue to trek higher and higher (with a few troughs along the way) and there is nothing to stop it because housing is a necessity, not a luxury and the majority of people would not trade the proximity factor where land is king.
On a side note, I have identified several other factors which will contribute to housing shortages (speaking of Melbourne again, although it probably applies to other cities)
1. there is still a huge housing supply problem in desirable locations (excluding new estate developments of course) given council redtape, inflated development levies and costs and banks unwillingness to lend for residential projects. For those interest rate hike advocates, it will only exacerbate the problem, as finance costs will ultimately squeeze profit margins
2. immigration is increasing and will continue to (the lifestyle of Australian cities is just too attractive to stop it). These guys have the cash and enough monetary and willpower to price out locals if need be
3. there is a large no. of upgraders and 2nd, 3rd homebuyers who are upgrading houses and building bigger houses, which alleviates sufficient land to build flats, apartments etc. within 15kms of the CBD
4. the big thing of 2009 and in many years to come is land bankers (especially Mainland Chinese investors - I know, because I am Chinese myself and intend to do the exact same thing, hahaha and have friends my age whose parents have bought properties in prestigious suburbs like Brighton, Canterbury etc. to just live vacant because they 'need' to get the money out of China). It may not make good logical and investment sense to just buy a property and live vacant for years but when it comes to dodging taxes, it very much does! and I heard that even local's are getting into the land banking business, in places like Ascot Vale, Footscray, Moonee Ponds and they are paying top dollars for any decent plot of land
5. government policy - if they had to choose, they would rather high property prices than increased housing affordability because they can tax more on capital gains, land tax etc...and the majority of people in this country are homeowners (whether it is the big mansion with tennis court, swimming pool and parading bikini girls to the 50sqm 1 bedroom flat out in whoop whoop) and not complaining first-home buyers. Existing homeowners would more than enjoy the current great health of the property market
6. Australian dream - need I say more?