FORTUNE — When Ben Bernanke launches a ship full of cash into the market where does it land? Answering that question might determine what stocks or bonds go up or down in the next few months.

Market observers seem increasingly sure that the Federal Reserve will reopen its money spigot. Earlier this week, two Morgan Stanley strategists including Vincent Reinhart, a former top Fed economist, said there was an 80% chance that the Fed will unveil some new effort to juice the economy soon.

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So investors will be listening closely on Thursday to Fed chairman Ben Bernanke testimony to Congress’ Joint Economic Committee on the state of the economy. While it’s unlikely that he will announce a new program immediately, many believe the chairman could hint at the fact that the Fed is considering what it could do next to help the economy. At the very least, Bernanke is likely to say the economy continues to struggle. Indeed, on Wednesday the Dow Jones industrial average (INDU) jumped nearly 300 points, its biggest one-day gain of the year, on news that the Fed was considering a new round of stimulus.

But some think investors might be overly optimistic about how much another stimulus effort from the Fed could boost their portfolio. The Fed has initiated two rounds of quantitative easing, which is when the central bank buys bonds in order to drive down interest rates, since the beginning of the financial crisis. One was started in November 2008 and ended in June 2010. The second, dubbed QE2, commenced in November 2010 and ended in June of last year. The Fed’s most recent stimulus effort is something called Operation Twist, where the central bank swaps short-term bonds in its portfolio for debt that comes due farther in the future. That started in September of last year and is set to end at the end of this month.

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Surprisingly, there appears to be few investments that have consistently benefited from the Fed’s stimulus efforts. Gold rose during the two QEs, but dropped during Operation Twist. High yield bonds and oil did the same. Private equity funds rose in value during QE2, but dropped during QE and Twist. Dividend paying stocks rose during all three periods, but the gains were relatively small, especially during QE.

The stock market in general have been a consistent winners under the Fed’s programs. But the gains from the QE and QE2 were in the single digits. Only Twist’s gains were impressive, with stocks up nearly 16% since last September. What’s more, Barry Knapp, the chief market strategist at Barclays Capital, thinks this may be a coincidence, and have nothing to do with Fed policy. He says the Fed has generally been late to act, not rolling out stimulus until well after the economy has actually slowed. In fact, Knapp says that generally the economy has been either rebounding or close to it before the Fed has taken its hands out of its pockets. Twist, for example, was started late last year, just at the time when the shocks of Washington’s debt deadlock, high gas prices, the Arab Spring and the Japanese Tsunami where receding. So Knapp thinks the economic and market rebound that happened after Twist was going to happen anyway.

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Of course, considering what did well, or didn’t, during the Fed’s stimulus efforts is more than just trader fodder. It may say something about the effectiveness of the programs. I could only find three things that rose or fell significantly in all three periods when the Fed had its foot on the peddle. Government bond yields have dropped to their lowest level in decades. Market volatility has dropped significantly in each of the three periods. Lastly, technology stocks have gone up consistently in all three stimulus efforts.

Of those three things, the move in technology shares is the most promising. But it’s unlikely that the tech sector alone would be large enough to swallow the 14 million people who want a job in this country and are out of work. And it’s not clear that we need the Fed to buy bonds to drop rates. Problems in Europe are causing investors to flock to U.S. bonds. Yields are dropping by themselves. That leaves us with lower market volatility, which is nice, and may boost some confidence in the economy, but if that’s all we’re getting from what appears to be the government’s main stimulus effort these days, then it’s clear we better start thinking of something else.

Correction: An earlier version of this story said the stock market had dropped during the period since the Federal Reserve announced Operation Twist. That was wrong. The S&P 500 is up 16% since the program was started in late September.