This book by Russell Napier is an excellent study of 4 20th century bear markets.
http://www.amazon.com/Anatomy-Bear-L...54576&sr= 8-1
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1921, '32, '49 and '82
A few interesting points.
1. Typically asset prices need to reinflate in order for the economy to start growing again. Napier points out that copper prices have been an excellent bellweather. Currently copper is at $1.36. It bottomed a few weeks ago at $1.25. Whether there will be further bottoms is obviously - at this point - unknown. Something to watch.
2. It is a myth that the market bottoms when there is no positive news. In the book, napier includes WSJ snippets in the months leading up to and following the market bottom. It is pretty clear that you first get some positive news stories and only then does the market rise.