Investors expect a new stimulus plan to be announced by the European Central Bank on Thursday. Reuters/Kai Pfaffenbach

The Dow Jones Industrial Average closed up slightly after a bouncy Wednesday session as investors anticipated a new stimulus plan from the European Central Bank on Thursday. ECB President Mario Draghi will speak to the media at 8:30 a.m. EST and is rumored to announce a $58 billion monthly program to inject more euros into the economy in an effort to stave off deflation, falling prices that discourage spending and investment.

"The ECB rumor was very important,” Phil Orlando, chief equity market strategist at Federated Investors in New York, told Reuters. “The market's perception was that Draghi was going to disappoint tomorrow in the magnitude" of how much the central bank would commit to its bond-purchasing program.

The Dow, which measures the share prices of 30 large industrial companies, closed up 39.05 points, or 0.22 percent, at 17,554.28. The S&P 500 stock index gained nearly 9.57 points, or 0.47 percent, to finish at 2,032.12. The Nasdaq Composite climbed 12.57 points, or 0.27 percent, to 4,667.42.

The ECB quantitative easing program, which is expected by many analysts to comprise around $690 billion over 12 months starting in March, increases public debt in return for more currency in the marketplace and freeing up lending from commercial banks. The move is aimed at spurring growth when slashing interest rates isn’t enough to do the job. U.S. companies would benefit from a strengthening eurozone economy.

But the program would generate a shift in investor assets that could weaken the euro, which would make exports more expensive to the massive trade bloc that’s home to Europe’s largest economies. The U.S. 10-year bond gained five basis points to 1.853 percent after dipping to 1.781 percent early in the session as investors sought the safe haven of U.S. bonds.