Economics
Although they are not personally liable for corporate debts, shareholders still bear the risk of loss should the company's stock decrease in value. However, they are also entitled to dividends, corporate profits minus the amount the company chooses to keep as retained earnings. A corporation can invest these retained earnings in the hope of generating larger profits. As the corporation becomes larger and more profitable, its stock value will likely increase, creating capital gains for shareholders. Hence, shareholders receive wealth from corporations in the form of both dividends and capital gains. When they expect both to increase, investors are more willing to purchase a corporation's stock. However, investors who expect a company to perform poorly are more likely to sell their stock and prospective investors are less willing to purchase it, decreasing demand for the stock while increasing supply. Consequently, the corporation's stock price will decrease.

Source: Bradley Schiller, The Economy Today (New York: McGraw-Hill/Irwin, 2006), pp. 678–681.