People who call a crash forget the willingness of the governments to break all the rules so as to keep the money flowing
Property used to increase (average) about 7 % per year so if you use that for a mean figure then the drop should be approx 45% but it will drop more than that and then recover over the next 10 years to reach the mean figure again
And as always there is such a huge rage in prices and quality of property that there is no actual price which reflects all property
ie you can have a select area where prices do not drop when all the suburbs around it go through the floor
The increase in asset value is only a factor when sold, but lots of people will be under water due to poor buying IMHO