This data comes from APM Australian property monitors. I can give you the breakdown of house and units but have combined them...no significant difference
There was 14000 properties for sale in jan 2007 17000 properties for sale in jan 2008 27000 properties for sale in feb 2008 The figures i received yesterday as at the end of april 2008 there are 30000+ properties for sale. The last month in WA had 35% more houses on the market than the previous.