The stock market hit a new milestone Monday.
Standard & Poor's 500 index rose above 2,000 for the first time as stocks climbed after news of corporate combinations and signals from central banks that easy-money policies won't soon end.
On Friday, Federal Reserve Chairwoman Janet L. Yellen said "the labor market has yet to fully recover" and resisted pressure to more quickly tighten monetary policy. European Central Bank President Mario Draghi also signaled Friday that the bank may inject further stimulus if needed.
"What these central banks are basically saying is, 'We are going to keep these rates down so go buy stocks,'" said Patrick J. O'Hare, chief market analyst with Briefing.com.
The bellwether index reached a high of 2,001.95 on Monday before falling below the 2,000 milestone. The index was up 9.74 points, or 0.49%, to 1,998.14 in afternoon trading.
Stocks also rose on merger and acquisition news.
On Sunday, Swiss pharmaceutical giant Roche said it has agreed to acquire Northern California biotech firm InterMune in an $8.3-billion deal.
Shares of InterMune climbed $19.10, or 35.50%, to $72.90 on Monday.
Also on Sunday, fast-food giant Burger King, based in Miami, and Canadian coffee-and-doughnut chain Tim Hortons said that merger discussions were underway and that a "new publicly-listed company would be headquartered in Canada, the largest market of the combined company."
Burger King shares rose 19.25%, $5.22, to $32.33.
The S&P 500 is up 9% since the start of the year.