* Initial claims drop 14,000 from prior week
* Family Dollar rejects Dollar General buyout offer
* Jackson Hole conference to begin
* Indexes up: Dow 0.42 pct, S&P 0.27 pct, Nasdaq 0.05 pct (Updates to market open; adds data, quote)
By Chuck Mikolajczak
NEW YORK, Aug 21 (Reuters) - U.S. stocks inched higher on Thursday and the S&P notched a record high as a flurry of data pointed to steady improvement in the economy and investors awaited the start of a meeting of top central bankers and economists in Jackson Hole, Wyoming.
Policymakers are due to discuss the labor markets of major economies at the Aug. 21-23 meeting, with U.S. Federal Reserve Chair Janet Yellen scheduled to speak Friday. Investors will peruse officials' remarks for clues on the timing of an interest rate hike.
The first of a string of economic data releases on Thursday came in the form of initial jobless claims, which fell to a seasonally adjusted 298,000 last week, a drop of 14,000 from the prior week, and slightly below the 300,000 estimate.
Financial data firm Markit said its preliminary or "flash" U.S. Manufacturing Purchasing Managers Index rose to 58 in August, its highest since April 2010, from 55.8 in July. Economists polled by Reuters expected a reading of 55.7.
In addition, existing home sales in July increased 2.4 percent to an annual rate of 5.15 million units, the fastest pace in almost a year, and the Philadelphia Federal Reserve Bank said its business activity index rose to 28.0, its highest level since March 2011.
"It seems that conditions reflect the best of all worlds - U.S. economic growth that is neither too slow, which would put pressure on earnings - nor too fast, implying inflationary pressures which could lead to P/E contraction and possibly accelerate the Fed's move towards higher interest rates," said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management in Minneapolis.
The Dow Jones industrial average rose 71.15 points or 0.42 percent, to 17,050.28, the S&P 500 gained 5.42 points or 0.27 percent, to 1,991.93 and the Nasdaq Composite added 2.08 points or 0.05 percent, to 4,528.56.
Hewlett-Packard gained 4.7 percent to $36.78 as the biggest boost to the S&P 500 after posting a surprise increase in quarterly revenue.
Family Dollar Stores Inc rejected Dollar General Corp's $8.95 billion acquisition offer, citing antitrust concerns, and reaffirmed its support for a buyout offer from Dollar Tree Inc.
Family Dollar shares shed 0.2 percent to $79.69 and Dollar General dipped 0.3 percent to $63.58. Dollar Tree also reported quarterly results and fell 1.4 percent to $54.25.
Sears Holdings tumbled 7.2 percent to $33.35 after the owner of Sears department stores and the Kmart discount chain reported a ninth straight quarterly loss and said it might close more stores than planned this year.
Editing by Bernadette Baum and Nick Zieminski