An epidemiologist calculating the risk of a localised epidemic becoming a global pandemic would investigate every possible channel of contagion from the infected region to the rest of the world. Focusing on, say, the incidence of close human contact would underestimate the pandemic risk if the...

Policy is only as good as the information at the disposal of policymakers. Few moments illustrate this better than the uncertainty before and after the default of Lehman Brothers and the subsequent decision to stand behind AIG. Authorities were forced to make critical policy decisions, despite...