How bad is the economy going to get?

Interesting article on the Freakonomics blog:

For example, using last Friday’s options prices, we can calculate that it would cost 10 cents to buy a portfolio of options that pays $1 if the S&P 500 falls below 250 on December 18, 2010. If markets were risk-neutral (I’ll come back to this), we could infer that the market thought there was a 10 percent probability that the value of U.S. stocks could fall to one-third their current value by the end of next year. Such a drop would leave the index down to one-sixth of its peak level in late 2007. By way of comparison, in the Great Depression the value of stocks fell to between one-sixth and one-seventh of their earlier values.

Well, at least it's only a 10% chance...