Roughly once a year, the managing director of the International Monetary Fund, the US treasury secretary and in some cases the finance ministers of other G-7 countries will get a call from the finance minister of a large emerging market economy. The emerging market finance minister will indicate that the country is rapidly running out of foreign reserves, that it has lost access to international capital markets and, perhaps, that is has lost the confidence of its own citizens. Without a rescue loan, it will be forced to devalue its currency and default either on its government debt or on...