By Victor Reklaitis and Sara Sjolin, MarketWatch

NEW YORK (MarketWatch) -- U.S. stocks edged up on the final day of the year, adding a bit more to their solid 2014 gains.

The S&P 500 (SPX) tacked on 2 points, or 0.1%, to 2,083, in Wednesday trade as the benchmark eyed a yearly advance of 12.7%, while the Dow Jones Industrial Average (DJI) moved up by 34 points, or 0.2%, to 18,017. The blue-chip gauge, now up 8.7% for the year, clambered back above 18,000 at the open after closing Tuesday under that big round number.

The tech-heavy Nasdaq Composite (RIXF) rose 15 points, or 0.3%, to 4,792, looking at a 2014 gain of 14.7%. The Russell 2000 (RUT) added 4 points, or 0.3%, to 1,217, and the small-cap index is on track for a yearly advance of 4.6%.

The year's gains have been driven largely by improving corporate earnings, steady improvements to the U.S. economy and a still-accommodative Federal Reserve, even as it is widely expected to begin raising interest rates in mid-2015. Wednesday's positive tone wasn't dented much by worse-than-anticipated readings for weekly jobless claims and Chicago-area business conditions. On the upside, a gauge of pending home sales rose 0.8% in November, topping expectations.

Both the New York Stock Exchange and Nasdaq will observe regular trading hours on Wednesday, closing at 4 p.m. Eastern. Trading is light ahead of the New Year's Day holiday, with volumes far off their 30-day moving average, according to FactSet data. Markets will reopen on Friday.

See: When do markets close on New Year's Eve?

Movers and shakers: Southwest Airlines Co.(LUV) performed best among S&P 500 stocks. Airlines are benefiting from plunging oil prices, and crude was down again Wednesday. The flip side of that trend -- energy stocks -- dragged on the market.

NephroGenex Inc.(NRX) soared after the small biotech late Tuesday announced positive safety study results for a diabetic nephropathy treatment.

Meadowbrook Insurance Group Inc. (MIG) also gained after news that China's Fosun International Ltd. will buy the U.S. insurer for $433 million.

(Read more about the day's movers here: http://www.marketwatch.com/story/nephrogenex-mimedx-in-focus-for-wednesday-2014-12-30.)

Other markets: In Asia, most markets ended higher, although Australia and New Zealand finished in the red. The stock markets in Japan, South Korea, Indonesia, Thailand and the Philippines were closed for New Year's Eve.

Trading was upbeat, but thin in Europe. German and Italian stock markets were closed.

The dollar (DXY) was little changed, keeping its yearly advance of more than 12% and on track for its best year since 2005, according to FactSet data. Oil prices slumped, while gold prices dropped.

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