* Consumer confidence data tops expectations
* Marvell Technology climbs after KKR reports stake
* Berkshire Hathaway to buy unit from Phillips 66
* Indexes up: Dow 0.21 pct, S&P 0.21 pct, Nasdaq 0.22 pct
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 Conference Board, an industry group, said its index of consumer attitudes rose to 78.1 from an upwardly revised 72.0 in November and above the expected 76.0 reading.
Data earlier in the day showed The S&P/Case Shiller composite index of 20 metropolitan areas gained 0.2 percent in October from September but posted the strongest annualized gain in October in more than seven years.
But the Institute for Supply Management-Chicago business barometer declined to 59.1 from 63.0 in November, falling short of economists' median forecast of 61.0. However, it remained above the 50 mark which indicates expansion.
"A little bit of a mixed economic picture today but the consumer confidence is probably the most important number of the bunch," said Tim Ghriskey, chief investment officer of Solaris Group in Bedford Hills, New York.
"The consumer confidence number is higher and definitely above expectations, strongly above November. Certainly a good indication and news like that on a quiet trading day is going to have a little bit bigger than outsized impact usually, so we've seen a nice jump on the averages."
The S&P 500 is up 29.3 percent for the year and the Dow is up nearly 26.2 percent for 2013, boosted in large part by stimulus from the Federal Reserve. The Fed recently announced it will trim its monthly bond purchases in response to an improving economic picture.
The Nasdaq is up 37.9 percent for the year, setting the technology-heavy index up for its best yearly performance since 2009.
The Dow Jones industrial average rose 34.52 points or 0.21 percent, to 16,538.81, the S&P 500 gained 3.89 points or 0.21 percent, to 1,844.96 and the Nasdaq Composite added 9.165 points or 0.22 percent, to 4,163.364.
For the month, the Dow is up 2.8 percent, the S&P has gained 2.2 percent and the Nasdaq has risen 2.6 percent.
Trading volume is once again expected to be light with U.S. markets closed Wednesday for the New Year's holiday. With many traders away, the thin volume could make for greater volatility.
Volume on Monday totaled 4.37 billion shares, well short of the 5.89 billion average so far this month, according to data from BATS Global Markets.
Marvell Technology Group Ltd jumped 5.5 percent to $14.52 after private equity firm KKR & Co LLP reported a 6.8 percent stake in the chipmaker, according to a regulatory filing.
Warren Buffett's Berkshire Hathaway Inc struck a deal for around $1.4 billion of stock to buy a Phillips 66 business that makes chemicals to improve the flow potential of pipelines. Phillips shares gained 2.5 percent to $76.72.
Hertz Global Holdings Inc surged 8 percent to $27.99 before the opening bell 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.