The world is afraid of a repeat of the deflation of the Great Depression. Deflation is a negative drop in prices caused by the contraction of money supply, the opposite of inflation. In 1932, US consumer prices fell 10 percent and between 1929 and 1933 fell 27 percent in total. Today despite inflation at 40 year lows, prices are still going up, not down. In the 12 months ended in August, prices rose 1.1 percent.