The world, over the course even of its relatively recent history, has known many natural disasters, including earthquakes, volcanic eruptions, tsunami, hurricanes, floods, droughts, and pandemics. The 1918-1919 Spanish flu pandemic killed more than 20 million people (some estimates run as high as 50 million). The current AIDS pandemic has already killed more than 20 million people (most in sub-Saharan Africa), and there are serious concerns that a new avian flu pandemic could kill hundreds of millions of people around the world. The recent earthquake in Pakistan is estimated to have killed over 70,000 people. The tsunami in the Indian Ocean in December 2004 killed 300,000 people (Winchester 2003; Winchester 2005; Barry 1997). Richard Posner, in his recent provocative book, Catastrophe (2004), worries about much more remote but more devastating natural disasters such as asteroid collisions with the earth or extreme forms of global warming followed by an ice age.