Investing.com -- U.S. stocks plummeted on Monday experiencing their worst session of the year, as catastrophic debt crises in Greece and Puerto Rico weighed on the major indices.
Less than 48 hours after the Greek parliament approved a July 5 referendum that could decide the nation's fate in the euro zone, Standard & Poor's downgraded Greece's credit to a CCC- from a previous rating of CCC. Unless Greece improves its economic outlook immeasurably, S&P indicated the nation is inevitably headed toward a default, adding that there is a 50-50 chance the nation will leave the euro.
Stocks on the Dow Jones Industrial Average plunged nearly 2% on Monday, suffering its worst one-day loss since June, 2013. The NASDAQ Composite index fell more than 120 points to dip below 5,000 while the S&P 500 Composite index also fell by more than 2% to move into negative territory for the year. The Dow lost 350.33 or 1.95% to 17,596.35 to erase all of its gains for 2015, while the NASDAQ dove 122.04 or 2.40% to 4,958.47, as Apple Inc (NASDAQ:AAPL) lagged.
The S&P 500 fell 43.85 or 2.09% to 2,057.64, as all 10 sectors closed in the red. Stocks in the Basic Materials, Financials and Health Care sectors lagged, each closing down by more than 2.3%.
A pair of bond insurers, Assured Guaranty Ltd (NYSE:AGO) and MBIA Inc (NYSE:MBI), saw their shares plunge after Puerto Rico governor Alejandro Garcia Padilla said it will be difficult for the island to pay a mountain of debt exceeding $70 billion. Both insurers reportedly have several billion in exposure to Puerto Rico's sovereign debt. Shares in Assured Guaranty fell more than 13% to 23.76, while shares in MBIA dropped more than 23% below 6.50.
All 30 components on the Dow closed in the red, including Wal-Mart Stores Inc (NYSE:WMT) the session's top performer. Shares in Wal-Mart fell 0.70 or 0.97% to 71.42. Wal-Mart shares are now down nearly 5% on the year. The worst performer was EI du Pont de Nemours and Company (NYSE:DD), which dipped 1.96 or 2.99% to 63.64 ahead of a potential spin-off of its performance chemicals division.
The biggest gainer on the NASDAQ was Catamaran, which inched up 0.02% to 61.09. The worst performer was Micron Technology Inc (NASDAQ:MU), which fell 0.93 or 4.73% to 18.73. Last week, the Boise, Idaho-based company lowered its forward guidance for the remainder of 2015 amid declining prices for semiconductor chips.
The top performer on the S&P 500 was Amphenol Corporation (NYSE:APH) which gained 1.16 or 2.08% to 56.84. The worst performer was Harman International Industries (NYSE:HAR), which fell 7.66 or 6.07% to 118.46.
Shares in Peabody Energy surged more than 9.5% after the U.S. Supreme Court overturned a landmark air quality law, ruling that the Environmental Protection Agency did not properly consider the costs of regulations on companies when it imposed new caps on emissions by coal and oil-fired power plants.
On the New York Stock Exchange, declining issues outnumbered advancers by a 2,911 to 303 margin.