NEW YORK ( TheStreet) -- U.S. markets closed lower Thursday as Philadelphia Fed President Charles Plosser warned that the central bank may be limited in its ability to implement further quantitative easing. The S&P 500 was down 0.37% to 1,626.67. Stocks dropped Thursday despite encouraging labor market data and a report that Microsoft ( MSFT) may buy Nook Media LLC, the digital book venture of Barnes & Noble ( BKS). Barnes & Noble soared 24% to $22.10 after TechCrunch, which is owned by AOL Inc. ( AOL), reported that Microsoft is offering to buy Nook for $1 billion. TechCrunch cited internal documents obtained by the technology news site. Microsoft dropped 1% to $32.66 while AOL, which was upgraded to "outperform" by Wells Fargo gained 3.4% to $39.04. "We set new records every day and when you get near the 1,630 area there's going to be some natural resistance," said JJ Kinahan, Chicago-based chief derivatives strategist at TD Ameritrade. "It's tough for a lot of companies at this point in the earnings cycle; we rallied so much that everyone almost has a suspicious eye to everything. For them, earnings have to blow away expectations ... it's a bit of a psychological game at this point." The Dow Jones Industrial Average dropped 0.15% to 15,082.62 while the Nasdaq was slipped 0.12% to 3,409.17. The Labor Department reported Thursday that weekly initial jobless claims dropped by 4,000 to 323,000, staying near a five-year low, in the week ended May 4 from and upwardly-revised 327,000 the prior week. The four-week moving average on initial claims was 336,750, a decrease of 6,250 from the previous week's 343,000. Continuing claims fell 27,000 to 3.005 million in the week ended April 27 from an upwardly-revised 3.032 million the preceding week. Economists, on average, were expecting continuing claims of 3.02 million and initial claims of 335,000. Precision Castparts ( PCP) was a big gainer in the S&P, advancing 7.6% to $206.68 after the manufacturer of metal components and products booked fourth-quarter earnings of $2.82 a share that beat estimates by seven cents, driven by growth in commercial OEM aerospace demand, steady improvement in industrial gas turbine spares, and accelerating oil and gas downhole casing production, along with a full quarter of strong Timet performance, the company said. The Census Bureau reported that wholesale inventories rose 0.4% in March versus the expected rise of 0.3% and decline of 0.3% in February. June gold futures fell $5.10 to $1,468.60 an ounce and June light sweet crude oil futures lost 23 cents to $96.39 a barrel. Follow @atwtseWritten by Andrea Tse and Joe Deaux in New York >To contact the writer of this article, click here: Andrea Tse.