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New York (CNN Money) Christmas may be over, but it seems Santa is still delivering good news for investors.

TheDow Jones industrial averageclosed at a record high for the 50th time this year. TheS&P 500also ended at a record high and theNasdaqmarked a new 13-year high.

U.S. markets were closed Wednesday for the Christmas holiday break. Trading volume has been below average, with many professional money managers taking the week off or working remotely.

Still, the week is turning out to be a good one for stocks, with not much bad news to stop investors from taking the market on an incredible year-end rally.

Over the past 100 years, the Dow has gained during the week of Christmas 68% of the time, according to Schaeffer's Investment Research.

Related: Fear & Greed Index gets greedy again

Markets have charted big gains this year. The Dow and S&P 500 are both up more than 20%, while the Nasdaq has soared over 30%.

The broad rally puts the Dow on track for its best year since 2003 and the S&P 500 on pace for its best year since 1997.

This year's gains have been driven by ongoingeconomic stimulusfrom the Federal Reserve, increased confidence in the economy, solid corporate earnings growth and more individual investors entering the stock market.

Related: China's $50 billion move to avert cash crunch

The Fed announced earlier this month that it will modestly reduce its bond buying program in January. But many experts believe the bull market, which began in early 2009, willcontinue for a sixth year in 2014, albeit at a more modest pace.

Meanwhile, the bond market continues to retreat. The yield on the 10-year Treasury note brieflytraded at 3%on Thursday, matching the highest level of the year.

On the economic front, initial claims for unemployment benefits fell last week, according to government data released Thursday.

Shares ofUPSandFedExwere little changed despite delays that caused both package delivery companies tomiss holiday deadlines.Amazonoffered a $20 gift card and also a refund of shipping charges for customers who did not receive their packages on time.

The problems with UPS come weeks after Amazon founderJeff Bezos unveiled plansto use unmanned aerial vehicles -- or drones -- to deliver small packages in four to five years.

"$AMZNbring on the drones move over$UPS," said StockTwits usertferraro5.

While the delays were a public relations headache for UPS, some traders see a sliver lining.

"$UPSis so busy they can't even get all their packages delivered? Sounds like profit to me," saidAcropolis.

Twittercontinued a spectacular rally. Shares of the social media company rose 5%. The stock has gained more than 76% in December and has more than doubled in price since its November IPO.

Some traders said the run is being driven by large institutional investors and that once they stop buying, Twitter shares will crash.

"$TWTRThis is going to fall. HARD. And those left holding after the big boys leave will be sorry..." saidmo_karney.

Others were predicting even more gains for Twitter, which is currently trading at just under $74 a share.

"$TWTRblue bird wants to see $80 before 2014," saidtecrider.

ManyEuropean and Asianmarkets were closed for Boxing Day. TheNikkeigained 1%. Japan's stock exchange is up 51% for the year, making it the best performing global benchmark.

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