The Nasdaq rose 38.54 to 2,282.02, and the Dow Jones industrial average gained 16.91 to 11,122.42.
Investors will be listening for any insight on monetary policy when Greenspan addresses the Economic Club of New York at 8:20 p.m. EDT Thursday. He is scheduled to speak about economic developments.
Investors already shrugged at the day's first economic news: jobless claims data. The number of new applications for jobless benefits rose last week, while the number of people remaining on unemployment rolls reached its highest level in more than six years, the government said.
"Although the weekly job numbers today are just that (weekly), the stock market will likely monitor the data closely due to the Federal Reserve's consistent dialogue and analysis of labor-market pressures," U.S. Bancorp Piper Jaffray market strategist Brian Belski said in a report.
Politics also weighed on investors' minds, as Vermont Sen. James Jeffords announced his decision to leave the Republican Party, handing control of the Senate to the Democrats.
The effect of the power shift in the U.S. Senate "will be industry by industry," Stanley Nabi, chairman of the investment policy committee at Credit Suisse Asset Management, told Reuters. "It is negative to pharmaceuticals; this is one industry that will be impacted, but it will not have an impact across the board."
In what little company news there was, Triquint Semiconductor stumbled $4.22 to $20.59 after a double dose of bad news. The company warned that its 2001 earnings will miss estimates; and Sawtek, Triquint's merger partner, also said it would report disappointing results. Sawtek was off $4.86 to $23.39.
Computer services provider Electronic Data Systems said on Wednesday it would acquire Structural Dynamics Research for $950 million, or $25 per share, in a cash deal. The move sent EDS shares down $2.85 to $61.93. Structural Dynamics Research was up $6.71 to $24.27.
Satellite television provider EchoStar Communications, off 73 cents to $33.30, is raising cash to launch a bid for Hughes Electronics in a move that could compete with News Corp., off 75 cents to $36.53, a source familiar with the matter told Reuters. Hughes, up 55 cents to $24.30, controls EchoStar's larger rival, DirecTV.
E-business software maker Kana Communications, which is merging with Broadbase Software, named Brett White as chief financial officer of the combined companies, to be known as Kana. Shares in Kana were off 4 cents to $2.11; Broadbase was down 1 cent to $2.09.
Amazon.com was up $1.15 to $16.75, AOL Time Warner shed 90 cents to $54.38, and Yahoo rose $1.10 to $21.54.
Cisco Systems gained 55 cents to $22.91, Intel rose 41 cents to $29.21, Microsoft rose $2.02 to $71.72, and Oracle gained 47 cents to $17.30.