The Dow Jones industrial average was up nine points, or less than 0.1 percent, at 16,487 in the first few minutes of trading Monday.
The Standard & Poor's 500 index was flat at 1,840. The Nasdaq composite was down 11 points, or 0.3 percent, at 4,145.
With just two days left in 2013, the S&P 500 is on track for an annual gain of 29 percent, its best year since 1997. With dividends included, it's up 32 percent.
Crocs jumped $1.70, or 13 percent, to $15.04 after the shoe maker said it was getting a $200 million investment from the private equity firm Blackstone.