IT IS ESTIMATED that in 2001 the U.S. current account deficit will reach $450 billion, or 4.4 percent of GDP, up from 3.6 percent in 1999. Current account balance was last achieved in 1991 (1981 if Gulf War–related special receipts are excluded for 1991). One has to go back to the two decades before 1914, a period of mass immigration and extensive infrastructure construction, to find deficits even approximately as large, relative to GDP, as those of recent years. The United States is reckoned, by global standards, to be a country relatively rich in capital. Why, then, is it importing more capital than ever before? Are deficits on this scale sustainable? Are they likely to be sustained?