* Consumer confidence index tops expectations
* Marvell Technology climbs after KKR reports stake
* Berkshire Hathaway to buy unit from Phillips 66
* Dow up 0.3 pct, S&P 500 up 0.3 pct, Nasdaq up 0.4 pct
By Curtis Skinner
NEW YORK, Dec 31 (Reuters) - U.S. stocks advanced modestly on Tuesday, boosted by a solid consumer confidence reading, keeping the S&P 500 on track for its best year since 1997 and the Dow on pace to record its best performance since 1995.
The S&P 500 is up 29.5 percent for the year and all 10 sector indexes will end the year in positive territory. The Dow is up 26 percent, as investors rode the Federal Reserve's extraordinary stimulus and expectations for improved growth in a year that had only the slightest of hiccups.
The Fed recently announced it will trim its monthly bond purchases in response to an improving economic picture, but that has still not deterred equities.
The Nasdaq is up 38.2 percent for the year, setting the technology-heavy index up for its best yearly performance since 2009.
Trading volume was once again light in U.S. markets, which will be closed Wednesday for the New Year's holiday.
As the year draws to a close, the S&P 500's 117 percent gain dating to Barack Obama's 2009 inauguration is the second-best gain during the first five years of any president's time in office, based on figures dating to the 1930s. The S&P rose 123 percent between Bill Clinton's 1993 inauguration and the end of 1997.
The Conference Board, an industry group, said its index of consumer confidence rose to 78.1 from an upwardly revised 72.0 in November and above the expected 76.0 reading.
"The market was kind of flat until the pieces of economic data came out, none of which were particularly exceptional, but it seemed to drive more buying," said Stephen Massocca, managing director at Wedbush Equity Management LLC in San Francisco.
Data earlier in the day showed that the S&P/Case-Shiller composite index of home prices in 20 metropolitan areas gained 0.2 percent in October from September, but posted the strongest annualized gain in October in more than seven years.
The Dow Jones industrial average rose 49.36 points or 0.30 percent, to 16,553.65. The S&P 500 gained 5.27 points or 0.29 percent, to 1,846.34. The Nasdaq Composite added 17.09 points or 0.41 percent, to 4,171.29.
For the month, the Dow is up 2.9 percent, the S&P 500 has gained 2.2 percent and the Nasdaq has risen 2.8 percent.
"Is this the final leg of what all the talking heads have been calling the 'Santa Claus rally'? Or are we going to continue this story into the new year due to the taper talk?" said Weston Boone, managing director of equity trading at Stifel Capital Markets in Baltimore.
Twitter Inc appeared to turn the corner on its steep two-day losing streak, posting gains of 4.3 percent to $63.17 by the afternoon. The stock's price had tumbled 17 percent between Thursday and Monday. Twitter was the third most traded New York Stock Exchange-listed company.
Marvell Technology Group Ltd jumped 5.5 percent to $14.51 after private equity firm KKR & Co LLP reported a 6.8 percent stake in the chipmaker, according to a regulatory filing.
Hertz Global Holdings Inc surged 9 percent to $28.23 after the company said it had adopted a one-year shareholder rights plan in response to "unusual and substantial activity" it has observed in its shares. Hertz was the second most actively traded New York Stock Exchange-listed company by the afternoon, behind only Bank of America.