Risk in the stock market
Understanding what the risks are can help you master your portfolio.
Earnings reports: The release of earnings to the public as required under securities laws is actually a significant risk and it's not just to disappointments. It works both ways.
The market isn't always open. Significant back log in buying or selling orders can spark a significant swing in price at the open of the session (9:30 e.s.t.).
Flawed system: this isn't about the market but rather the connection of the market to portfolio decisions.