Is first-day market drop an omen? Yes and no

As goes the first trading day in January, so goes nothing else in particular. But if January is down, the rest of the year often follows.

The Standard and Poor's 500 stock index fell 0.89% on the first trading day of the year, the first first-day loss for the index since 2008, says Howard Silverblatt, S&P's index wizard. How much significance does that hold? Not a lot, Silverblatt says. Going back 85 years, January and the first day of the year have moved in the same direction 50.59% of the time — which is to say, about the same as flipping a coin.

Investors have a good reason to sell at the beginning of the year. The taxes on any gains they realize will be due April 15, 2015. Had they sold on Dec. 31, the taxes on those gains would have been due April 15 of this year.

Even though tax-selling can go on for a while, the entire month of January is a good barometer of where the rest of the year will go, Silverblatt says. When the S&P 500 has recorded a gain in January, it's has been up for the year 72.94% of the time, Silverblatt says.

Looking for an early warning system? The first five trading days of January will give a decent indicator as well, according to The Stock Trader's Almanac.

Writing in the 2013 Almanac, Jeffrey Hirsch and Yale Hirsch noted that in the past 39 years, when the first five days of January were positive, the S&P 500 was up for the year 84.6% of the time. The index jumped 2.2% the first five days of 2013, and soared 29.6% last year.