Investors who try to time their investments with stock exchange movements have much more to lose than to gain, says Vincent Fournier, portfolio manager at Claret. He explains that many factors must be reunited in order to sell at the peak and then buy back at the bottom. We must predict correctly when markets will begin their correction, the magnitude of the fall and the velocity at which indices will hit the bottom before they start rising again. An almost impossible task even for the most informed investor.