Experienced traders generally keep abreast of news concerning the businesses in which they have an open position, but that is not to say that the market will always respond to developments in the way that would normally be predicted.
So for example, let’s imagine that a company has just been through a difficult three month period, and announced a large drop in sales. You might conclude that the firm’s share price would drop as a result. Yet should the firm announce that they are planning to buy-back a significant number of shares simultaneously, then there’s a good chance that the stock price might actually increase. Traders who only focused on the news regarding the disappointing quarterly results could therefore possibly make a loss if the stock price moves in the opposite direction to the way which they assumed it would go.