Another aspect of the housing bubble has to do with a sudden burst of selling in a (relatively) small area. For example, say you have a large number of workers for a particular industry centered in one geographic area. A downturn in this industry could cause a lot of jobs to be outsourced, downsized, whatever term you wish to use. Those people can no longer afford the mortgages for those houses, and they all go on the market at once. No one wants to buy them because of the inflated price and lack of jobs in the area...