Why 2015 market looks too good to be true
Reuters/David Gray · CNBC

2015 by most accounts is expected to be a good, but not a great year for the stock market.

The U.S. stock market however, unlike others around the world, is expected to enjoy a "just right" environment of improving growth against a backdrop of tame inflation, low energy prices and low interest rates. It sounds too good to be true, but then again so did 2014's stock market, which closed out year with solid gains. The Dow (Dow Jones Global Indexes: .DJI) ended the year up 7.52 percent, helped by a fourth-quarter gain of 4.58 percent, while the Nasdaq (^IXIC) and S&P 500 (^GSPC) rose 13.40 percent and 11.39 percent, respectively, for the year.

"This is the most unbelievable market of my life," said Nuveen Asset Management's chief equity strategist, Bob Doll, in a recent interview. "I think '15 is going to be the year we move from disbelief to belief." The average 2015 forecast of 15 top Wall Street strategists is for a roughly 7.5 percent gain in the S&P 500 to 2,220, fairly modest, but still a decent showing on top of 2014's advance. Underlying those forecasts are also expectations for more volatility, particularly when the Fed moves to raise short-term interest rates.

Read More Here's what will drive stocks higher next year Ed Keon, portfolio manager at Quantitative Management Associates, said two factors helped 2014's stock market performance. One was that long-term rates stayed surprisingly low, and the 10-year, starting 2014 with a yield of 3 percent, is ending the year at around 2.16 percent. The other factor was a shocking more than 50 percent drop in the price of crude oil, a boost to consumers. U.S. crude futures settled Wednesday at $53.27 per barrel. "I think it's going to be another good year for the market, and a very good year for the U.S. economy," said Keon. "This might be the first year the improvement in the economy is felt by a broader group of people." The economy certainly has surprised on the upside recently, with third-quarter GDP increasing at an annual rate of 5 percent, on top of the second quarter's 4.6 percent growth rate. Economists have been revising growth forecasts higher but not near those levels.

On Wednesday, Citigroup said it now sees fourth-quarter growth at 3 percent and first-quarter 2015 growth at 4 percent. "A wide array of economic data has shown a clear pickup in momentum at the end of the year. The uptrend in payroll gains suggests a boost to personal income, factory output has soared and consumers have responded to widespread holiday discounting among retailers. We anticipate a further boost to consumer spending in coming months, due to diminishing energy costs," Citigroup economists wrote.