Research by the McKinsey Global Institute suggests roughly one-third of the U.S. current account deficit results from trade with U.S.-owned subsidiaries abroad.
This is a major reason why the dollar's broad-based slide on global foreign exchanges over more than three years hasn't narrowed the U.S. trade deficit, as conventional economic theory suggests it should.
The dollar has lost around a third of its nominal value against a basket of its major counterparts since January 2002, which should have made U.S. exports nominally cheaper and imports more expensive.
Yet U.S. consumers' voracious appetite to consume has seen the trade deficit balloon to new record after record. "In the real world, the J-curve doesn't exist anymore," said Quinlan at Banc of America Capital Management.
It typically takes around 18 months to two years for the J-curve effect to start showing. But if the dollar's decline is to eventually narrow the U.S. trade deficit, it will have to accelerate even more than it has so far.
"In our view, significant dollar depreciation is required simply to prevent further deterioration in the current account deficit," wrote Deutsche Bank's New York-based currency startegy team in a recent research note.
But while few would argue the extended lag effect of the J-curve, not everyone's convinced related-party trade diminishes U.S. financing needs or distorts the overall trade picture.
"You still have the same financial flows," said Peter Moricci, professor of business at Robert H.Smith School of Business, the University of Maryland. "It doesn't change the accounting and financing requirement."
For example, a U.S. automaker still needs foreign exchange to run its production plants abroad, Moricci said.