NEW YORK ( TheStreet) -- Major U.S. stock markets closed lower Monday as the excitement of corporate dealmaking led by Yahoo! ( YHOO) was offset by investor concern that the Federal Reserve may curb its bond-buying economic stimulus program. The S&P 500 closed off 0.07% to 1,666.29 while the Dow Jones Industrial Average lost 0.12% to 15,335.51. The Nasdaq slid 0.07% to 3,496.43. The Fed's Open Market Committee is expected to publish its minutes on Wednesday offering investors clues about whether the central bank plans to continue buying roughly $85 billion in assets each month to stimulate the U.S. economy. Conservatives among the bank's presidents have dominated the conversation in recent weeks, warning that the program is adding to inflation while holding back economic growth. The day's trading session was otherwise dominated by the announcement that Yahoo! plans to acquire the privately-held blog network Tumblr in a deal valued at $1.1 billion, while drugmaker Actavis ( ACT) said it plans to acquire specialty pharmaceuticals firm Warner Chilcott ( WCRX) for $8.5 billion in stock and assumed debt. Also see: Yahoo! 'Tumbling' Down the Right but Expensive Path Yahoo! added 0.2% to $26.58 as Warner Chilcott ( WCRX) rose 2% to $19.60 and Actavis ( ACT) gained 1.3% to $127.15. Chicago Federal Reserve president Charles Evans, a FOMC voting member, spoke on Monday at the CFA Society Chicago Distinguished Speakers Series and said that the Fed has acted appropriately in guiding the economy. New York Fed President Bill Dudley is expected to speak on Tuesday. On Wednesday, Federal Reserve Chairman Ben Bernanke will testify on the outlook for the U.S. economy before the Joint Economic Committee of Congress. Later that day, the FOMC will release minutes from its April 30 to May 1 meeting. Thomson Reuters reported that there have been 74 negative EPS preannouncements issued by S&P 500 corporations for the second quarter 2013, compared to 12 positive EPS preannouncements, resulting in a negative to positive ratio of 6.2 for the S&P 500 Index; if this persists, it would be the most negative of this ratio since the first quarter of 2001, according to Thomson Reuters. The report also said that 67% of the 463 companies in the S&P 500 have reported first-quarter earnings above analysts' expectations, which is higher than the long-term average of 63% and matches the average over the past four quarters of 67% as companies manage to squeeze out better-than-expected earnings through measures including cost-cutting, hurting the outlook on hiring and possibly the economy in future quarters. Only 47% of companies that released results reported first quarter revenue above analyst expectations, which is lower than the long-term average of 62% and lower than the average over the past four quarters of 52%, the report noted.