do, however, remain relatively unconcerned about imbalances and there have been assertions, such as by Michael P. Dooley, David Folkerts-Landau and Peter Garber, that nations need to avoid the temptation to switch to protectionism as a means to correct imbalances. Current account surpluses coincide with current account deficits of other countries, the indebtedness of the latter therefore increasing. According to Balances Mechanics by Wolfgang Stützel this is described as surplus of expenses over revenues. Increasing imbalances in foreign trade are critically discussed as a possible cause of the financial crisis since 2007. Many Keynesian economists consider the existing differences between the current accounts in the eurozone to be the root cause of the Euro crisis, for instance Heiner Flassbeck, Paul Krugman or Joseph Stiglitz. Causes of BoP imbalances There are conflicting views as to the primary cause of BoP imbalances, with much attention on the US which currently has by far the biggest deficit. The conventional view is that current account factors are the primary cause – these include the exchange rate, the government's fiscal deficit, business competitiveness, and private behaviour such as the willingness of consumers to go into debt to finance extra consumption. An alternative view, argued at length in a 2005 paper by Ben Bernanke, is that the primary driver is the capital account, where a global savings glut caused by savers in surplus countries, runs ahead of the available investment opportunities, and is pushed into the US resulting in excess consumption and asset price inflation. Reserve asset In the context of BoP and international monetary systems, the reserve asset is the currency or other store of value that is primarily used by nations for their foreign reserves. BoP imbalances tend to manifest as hoards of the reserve asset being amassed by surplus countries, with deficit countries building debts denominated in the reserve asset or at least depleting their supply. Under a gold standard, the reserve asset for all members of the standard is gold. In the Bretton Woods system, either gold or the U.S. dollar could serve as the reserve asset, though its smooth operation depended on countries apart from the US choosing to keep most of their holdings in dollars. Following the ending of Bretton Woods, there has been no de jure reserve asset, but the US dollar has remained by far the principal de facto reserve. Global reserves rose sharply in the first decade