It looks like the U.S. house price decline is already worse than the great depression:

http://www.boston.com/realestate/news/blogs/renow/2008/05/worse_than_the.html

“The chart, at right, shows that prices could fall further in 2008 than during the worst year of the twentieth century, 1932, when prices fell 10.5 percent. Prices at the end of March this year were 14.1 percent below prices at the end of March last year.”

Neat chart at the link.