The U.S. markets opened slightly lower today, as investors seemed focused on interpreting Federal Reserve Chairwoman Janet Yellen's comments on interest rates hikes. Weekly jobless claims, released ahead of the opening bell, rose by less than expected, with the four-week average trend ticking lower. Investors await more economic reports on the health of the housing market and manufacturing after the market open. The S&P 500 opened 1.6 points, or 0.1%, lower at 1,859.37. The Dow Jones Industrial Average dropped 24 points, or 0.1%, to 16,196.90 at the open. The Nasdaq Composite was down 4 points, or 0.1%, at 4,303.66.