Few will argue that a surprise, both positive and negative, can violently move the price of a security. A few examples include: http://stockcharts.com/school/data/media/chart_school/overview/whyanalyze-lu.png http://stockcharts.com/school/data/media/chart_school/overview/whyanalyze-aol.png http://stockcharts.com/school/data/media/chart_school/overview/whyanalyze-anf.png