In the ten-year stretch from Sept. 1929 to Sept. 1939, spanning the worst years of the Great Depression, the stock market dropped a full 50%, adjusted for inflation. Look out, the current decade (Feb. 17, 1999 to Feb. 17, 2009) appears to yield the same decrease: the Standard & Poor’s 500 stock index is down roughly 50%, also adjusted for inflation. read more »