“We hear a lot about “worst-case” projections, but they often turn out not to be negative enough. I tell my father’s story of the gambler who lost regularly. One day he heard about a race with only one horse in it, so he bet the rent money. Halfway around the track, the horse jumped over the fence and ran away. Invariably things can get worse than people expect. Maybe “worst-case” means “the worst we’ve seen in the past.” But that doesn’t mean things can’t be worse in the future. In 2007, many people’s worst-case assumptions were exceeded.”