Such a calendar effect flies in the face of the idea that financial markets are efficient. After all, asset prices ought only to move in response to new information . Predictable fluctuations should be identified, exploited and arbitraged away by traders. Since 1928, the ratio of monthly gains to losses in America’s s&p 500 index, excluding September, has been about 60/40. But the autumn chill seems to do something to the market’s psyche. In September the index has dropped 55% of the time. True to form, after a jittery August it has spent recent weeks falling. What is you take on falling financial markets ?