the gold standard. Prices will be reduced, making its exports more competitive, and thus correcting the imbalance. While the gold standard is generally considered to have been successful up until 1914, correction by deflation to the degree required by the large imbalances that arose after WWI proved painful, with deflationary policies contributing to prolonged unemployment but not re-establishing balance. Apart from the US most former members had left the gold standard by the mid-1930s. A possible method for surplus countries such as Germany to contribute to re-balancing efforts when exchange rate adjustment is not suitable, is to increase its level of internal demand (i.e. its spending on goods). While a current account surplus is commonly understood as the excess of earnings over spending, an alternative expression is that it is the excess of savings over investment. That is: where CA = current account, NS = national savings (private plus government sector), NI = national investment. If a nation is earning more than it spends the net effect will be to build up savings, except to the extent that those savings are being used for investment. If consumers can be encouraged to spend more instead of saving; or if the government runs a fiscal deficit to offset private savings; or if the corporate sector divert more of their profits to investment, then any current account surplus will tend to be reduced. However, in 2009 Germany amended its constitution to prohibit running a deficit greater than 0.35% of its GDP and calls to reduce its surplus by increasing demand have not been welcome by officials, adding to fears that the 2010s would not be an easy decade for the eurozone. In their April 2010 world economic outlook report, the IMF presented a study showing how with the right choice of policy options governments can shift away from a sustained current account surplus with no negative effect on growth and with a positive impact on unemployment. Rules based rebalancing mechanisms Nations can agree to fix their exchange rates against each other, and then correct any imbalances that arise by rules based and negotiated exchange rate changes and other methods. The Bretton Woods system of fixed but adjustable exchange rates was an example of a rules based system. John Maynard Keynes, one of the architects of the Bretton Woods system had wanted additional rules to encourage surplus countries to share the burden of rebalancing,