S&P 500 index rises for 9th quarter in a row, 4th such streak since WWII

The bull market slowed to a trot but didn't stop this winter.

Stocks have been buffeted since the start of the year by plunging oil prices, a surging dollar and worries about the timing of a potential rate increase by the Federal Reserve. None of that has been enough to keep the market from logging a small gain in the first three months of the year.

It is the ninth straight quarter that the Standard & Poor's 500 index has risen. The index has only had three other stretches that long since World War II.

That's good news for bulls because the previous three times the market notched a nine-quarter winning streak, the S&P 500 index averaged an increase of 8.1 percent in the 10th quarter.

During the latest quarter, the index climbed 0.4 percent. The gain follows an 11 percent jump in 2014 and a 30 percent surge in 2013.

The three-month stretch also included some big milestones.

The bull market in stocks turned six in early March. The S&P 500 index has more than tripled since bottoming out at 676.53 on March 9, 2009.

Another achievement was the tech-focused Nasdaq closing above 5,000 on March 2, for the first time since the peak of the dot-com bubble 15 years ago. The index ended the quarter at 4,900.88 and remains short of its all-time closing high of 5,048.62, reached March 10, 2000.

Investors have kept bidding stocks higher because the U.S. economy continues its slow but steady growth, company earnings have continued to rise and rally-killers like inflation and sharp interest-rate increases aren't on the horizon.

"When you put it all together, it seems like it's still a positive environment for stocks," says Stephen Freedman, senior investment strategist at UBS Wealth Management Americas.

Here's what helped and what hurt stocks in the first quarter.

HELPED:

— THE FED: Investors were watching the Fed even more intently than usual from January through March.

Policy-makers have kept the Fed's benchmark interest rate close to zero for more than six years to boost borrowing and lending and help the economy recover from a deep recession that lasted from 2007 to 2009. That backdrop has helped stocks climb.

A strong jobs report in March left many investors thinking that the Fed would begin raising rates in June, and stocks fell.

But the Fed surprised investors after its policy meeting later in the month. Policy-makers gave a downbeat assessment of the U.S. economy and implied that the pace of any rate increases would likely be more gradual than they had previously forecast. Stocks rallied.

— EARNINGS GROWTH: Earnings for S&P 500 companies grew 7.8 percent in the final three months of last year, according to S&P Capital IQ. That's part of a long stretch of profit growth, which has helped push stocks higher. The last time earnings contracted was in the third quarter of 2009, the data provider says.

The best month in the quarter was February, when stocks rallied 5.5 percent as companies reported their earnings for 2014.

— HEALTH CARE: Health care stocks were the stars of the show, thanks in part to a wave of mergers in the industry.

The sector gained 6 percent in the quarter, the best performance among the ten industry groups that make up the S&P 500 index. The sector has outperformed the broader index for the last four years.

HURT:

— DOLLAR MOVES: The dollar has been climbing for about a year now, but the pace of gains accelerated in the first quarter.

The U.S. currency surged 10 percent against the euro in the period as investors anticipated higher rates and unemployment continued to fall. At the same time, the European Central Bank started a bond-buying program to keep rates low and boost growth in the region.

A rising dollar is a negative for U.S. companies. Almost half of the revenue for companies in the S&P 500 index comes from overseas. A stronger dollar makes goods produced in the U.S. more expensive for buyers in other countries. It also reduces the value of the profits earned abroad when they're converted back into dollars.

The stronger dollar will reduce the average earnings of S&P 500 companies by about $5 per share, or 4 percent, this year, Deutsche Bank estimates.

— OIL: A 9 percent slump in the price of oil weighed on stocks in January. U.S. crude fell below $45 a barrel that month, which at the time was the lowest price in more than six years. Investors worried that the sharp decline in prices signaled a slowdown in demand, and was worrisome sign for the global economy.

— POWER OUTAGE: Utilities fell the most in the S&P 500 in the first quarter, dropping 6 percent. The sector had a strong 2014 as investors bought the dividend-rich stocks for income as the yields on bonds fell.

But the market has changed. Even though rates aren't expected to rise as much as previously thought, most economists and analysts do expect them to go higher. When that happens, bond yields will also rise. Utility stocks will be less attractive by comparison.