Traders and strategists say the market rally is likely to continue through December for a deceptively simple reason: Stocks have rallied significantly all year, and those gains are likely to beget further gains.
The market "should do pretty well into the end of the year," writes Nicholas Colas, chief market strategist at ConvergEx Group. "There's plenty of cash that probably feels it should get off the bench, and so many managers have underperformed in 2013 that many of them will probably want to look fully invested by December 31."
In other words, since most fund managers have returned less than the market, there will be a temptation to buy into the end of the year to try to capture some last-minute gains—or at least make it look like they have owned the winners all year.
"Year-end melt-up, here we come," Colas continued in a recent note.
After all, owning anything other than stocks has not been a winning maneuver in 2013.
"Commodities and bonds have given investors little or no return this year, while the S&P is up 20 percent," points out Anthony Grisanti of GRZ Energy and a CNBC contributor. "If you would have invested in gold over the same period, you would be down over 20 percent."