Long Term Dow

Here's a really helpful 100 year (well, almost) chart of the Dow Jones Industrial Index.

Interestingly, it shows that during the Great Depression, the absolute lowest Price to Book of the Dow was about 0.55x (during 1931), and the average Price to Book for that year was about 0.9x.
This suggests that even if the world falls apart, the US S&P 500 can fall about 50% to 75% from its current price to book of 1.8x. This comes as a bit of a surprise to me. I thought Great Depression prices would be even cheaper.

Anyway, here it is. Like I said, its really helpful:

Update: The Dow's remarkable Great Depression rally between 1931 to 1937 (41 points to 200 points, or +400%) would have left me gobsmacked were I living during the period. Subsequently, the index crashed and it took another 15 years (1951) for the Dow to break out from the 200 points level. This was largely because of World War II.