Gains came easily for U.S. stock investors in 2006, as long as they were not scared off by a sharp sell-off in the middle of the year.

All four major indexes -- the Dow Jones Industrials, the Standard & Poor's 500, the Nasdaq Composite and the Russell 2000 -- ended the year with double-digit percentage gains.

Of the 10 major industry groups of the S&P 500, not a single one ended the year in the red. In a swift reversal, telecommunications, the worst performer of 2005, led the pack in 2006 with a hearty 32.1 percent gain. Even healthcare, the year's worst performer, gained 5.8 percent -- more than it did in 2005 when it ranked third.

To be sure, investors could have done even better if they put their money abroad. The Morgan Stanley Capital International All Country World Index <.MSCIWD> gained 19 percent against the S&P 500's 14.1 percent rise. The pan-European FTSEurofirst 300 <.FTEU3> gained 16.5 percent, and the MSCI Emerging Markets Index <.MSCIEF> climbed 28.8 percent.

The year, however, was not all smooth sailing. In mid-May there were hardly any safe harbors when markets around the world plunged, with high-flying emerging markets among the steepest decliners. During that period all three major U.S. indexes fell into negative territory for the year.

But robust corporate earnings, ongoing corporate mergers and private equity buyouts, plus economic data that was neither too strong, nor too weak, set stocks back on an upward track, with the S&P 500 posting six straight months of gains.

"The market is probably pleasantly surprised just because of the way we started," said Brian Williamson, vice president, equity trading, The Boston Co. Asset Management. "You had a low right in the dead middle of the year and since then it's been gangbusters. If you've been in it since July you're probably pretty happy now."