A liquidity trap is a Keynesian theory that a situation can develop in which interest rates reach near zero (ZIRP) yet do not effectively stimulate the economy. In theory, near-zero interest rates should encourage firms and consumers to borrow and spend. However, if too many individuals or corporations focus on saving or paying down debt rather than spending, lower interest rates have less effect on investment and consumption behavior; the lower interest rates are like "pushing on a string." Economist Paul Krugman described the U.S. 2009 recession and Japan's lost decade as liquidity traps. One remedy to a liquidity trap is expanding the money supply via quantitative easing or other techniques in which money is effectively printed to purchase assets, thereby creating inflationary expectations that cause savers to begin spending again. Government stimulus spending and mercantilist policies to stimulate exports and reduce imports are other techniques to stimulate demand. He estimated in March 2010 that developed countries representing 70% of the world's GDP were caught in a liquidity trap.