NEW YORK ( TheStreet) -- If the stock market's volatile performance so far this month tells us anything about the rest of 2015, expect a hair-raising year with only modest gains.

In the first two weeks of trading this year, the S&P 500 has fallen eight out of 10 trading sessions. The swings have been wide, ranging from 219 to 425 points in the Dow Jones Industrial Average in a single day, averaging almost 290 points daily. 

Since January is often considered a bellwether for the rest of the year, what can we expect for the rest of the year? Here's what we know.

"January is a very good predictor if the market is up," says Sam Stovall, chief investment strategist for Standard & Poor's Equity Research Services, referring to the so-called January barometer. "Since World II, whenever January was up the market rose in the remaining months of the year about 85% of the time and it gained on average more than 11%."

But if the market is down in January "it's a coin toss," says Randy Frederick, managing director of trading and derivatives at Charles Schwab. "Since 1950, when January is down the year is up 48% of the time and down 48% of the time."

 There are reasons to be bullish about 2015:

  • It follows a "good year" in 2014 (the S&P gained 11%) and stocks rise two-thirds of the time following good years, averaging just over 6%, says Stovall.
  • Similar gains also occur in the third year of a U.S. president's second term, like the one we're in now, even after pullbacks, corrections or bear markets.
But there are also reasons to be bearish:
  • This bull market is longer than most. Come March it will be entering its seventh year and only two out of 11 post-World War II bull markets completed their seventh year, says Stovall.
  • The market is overdue a correction of 10% of more because it's gone 39 months without one -- the average interim is 18 months, says Stovall.

The strategists and analysts we talked to expect stocks will post modest gains this year in the mid-single digits because despite the market's drop so far -- it's down about 3% -- the U.S. economy continues to advance, interest rates will remain low even if the Federal Reserve raises rates later this year as expected and lower oil prices puts more money into consumers' pockets to spend.

Even though the global economy is struggling and the World Bank lowered its forecast, global growth is still expected to be positive this year, growing 3%, down from an earlier estimate of 3.4%.

Market strategists and analysts are more certain about the outlook for volatility than the outlook for market performance because the daily trading ranges have been wide. The VIX  (VIX.X) index, which measures volatility, is now at 22.4 -- well above the 20.2 average going back to 1990.

"We're having a volatile January and we will have a volatile year," says Nicolas Colas, chief market strategist at ConvergEx, a brokerage. Year seven of a bull market tends to be the second-most volatile, according to Stovall.

Frederick says the increased volatility provides "short-term trading opportunities" for investors to buy on dips, and recent history supports that. The S&P has now dipped below its 100-day moving average 10 times in the last two years, and eight of the last nine times it rallied to all-time highs afterward, says Frederick.

Colas suggests investors maintain their exposure to bonds because rates are trending lower, which should also help stock valuations. He also suggests investors buy utilities -- a bond substitute -- and technology shares. "Technology is gaining a bigger share of consumers wallets," says Colas, and those wallets are getting fatter because of lower oil prices.