"There was this incredible liquidity" flooding onto Wall Street from oil exporters, China and other emerging nations during the years when revenues were booming earlier this decade, said Doug Rediker, co-director of the Global Strategic Finance Initiative at the New America Foundation.

Through lopsided trade deficits with China and oil-exporting nations, "the U.S. was exporting [dollars] to other countries, and they needed to do something with them. They had to put the money to work" by investing in U.S. markets, Mr. Rediker said. LINK