Bank panics have always mattered because they create serious disruptions in economic and financial activity, depressing national economies. But they matter even more now, as information and communications technologies have stitched together a global financial system that is more vulnerable to crisis on a large scale. For example, the global bank panic of 2007-08 froze up the national economies of the U.S., England, France, Iceland, Ireland, and Germany -- all at the same time. And each of their governments had to act to bail out their own banks, without a consistent international...