The Dow Jones Industrial Average plunged 500 points, its second straight drop of that size and its fourth big decline this month, the AP reports. Longtime market favorites like Microsoft and Amazon took heavy losses Monday. Health care companies also fell sharply. A measure of small-company stocks fell into a bear market, a decline of 20% below their recent peak. The market is now well into the red for the year and the S&P 500 index is trading at its lowest level since October 2017. The S&P 500 fell 54 points, or 2.1%, to 2,545. The Dow lost 507 points, or 2.1%, to 23,592. The Nasdaq composite lost 156 points, or 2.3%, to 6,753. (More stock market stories.)