It’s been over a year since the Fukushima nuclear accident, and two years since the Deepwater Horizon oil spill. The financial crisis that led to the Great Recession unfolded almost four years ago. And, unbelieveably, over a decade has passed since the tragedy of 9/11. It is human nature, and the nature of time and memory, for these events to recede in the mind as they recede into history. But for businesses, knowing when to expend time and effort preventing — and planning responses to — low probability, high consequence events is now, more than ever, one of the hardest and most important risk management problems to address.