I think 40 – 50% is a good number. Cycles typically last 7 to 10 years from peak to peak. If we hit the bottom 3 to 5 years from now, inflation is not going to soften the blow that much. It would be strange if prices did not start rising until 2016 (down for 5 and flat for 5), as a previous poster suggested.
I think the correction to mean will be much swifter than that.