The
LA Times has a good run down on the subject, utilizing past data to predict the bottom of the market.
Each housing bust also has different fundamental characteristics making them harder to predict and compare. For example, part of the reason for the current housing bubble was subprime mortgages while in the early 90's a recession caused the price correction.
But in general, it is hard to predict when the market will hit rock bottom as conditions that affect it the most, such as the financial markets,government policy and availability of capital change continuously.
Hope this helps.