A falling dollar is normally good for the developing world. Because poor countries borrow more in the greenback than rich ones, their debt bills become less burdensome. At the same time, imports become cheaper, providing a balm to foreign reserves that are often stretched, and investors become more optimistic. So it was from 1971 to 1978 (the last time poor countries really splurged on infrastructure) and from 2004 to 2008 (when commodity exporters became unexpectedly flush).