It's not irrational. The traders essentially control the stock market and call the shots by manipulating the market into a favorable position then sell the stoc

It's not irrational. The traders essentially control the stock market and call the shots by manipulating the market into a favorable position then sell the stock. A glut of shares appearing on the market would thus drive the price down. The term is called "profit taking". http://www.investopedia.com/terms/p/profittaking.asp http://www.investopedia.com/terms/p/profittaking.asp