US dollar owes its strength to one simple thing: the world's need to repay a mountain of debt

``... the availability of cheap dollars may have resulted in dollar-denominated debt-financed investment decisions which now seem less economically well-grounded. For example, oil projects financed by dollar debt and predicated on a projected price of US$100 a barrel look a lot less economically sustainable when the price of crude has fallen by half. Yet the money has still been borrowed and the lenders expect to get repaid both interest and principal.''