The common belief holds that a lower corporate tax rate would prompt a healthy economic boost.

Prompted by a lower tax rate, U.S. corporations would bring home, or repatriate, the billions of dollars they hold in offshore tax havens, and invest the money in the U.S. economy.

But that's just a myth, tax expert Edward Kleinbard told CNNMoney. The offshore corporate funds, which may be up to $1.8 trillion, is not "trapped" overseas and the economic benefits of repatriated funds are questionable.

Editor's Note: How to Pay Zero Taxes . . . Legally

Much of that money is already invested in the United States in a somewhat roundabout way, since it's often invested in U.S. bonds, stocks and bank deposits, he noted.

A study of 27 large U.S. corporations in 2011 found that 46 percent of the offshore funds these companies have, or $250 billion, are already in U.S. bank accounts, bonds or mutual funds.

Corporations often say they would repatriate their foreign funds if they only got a tax break.

"They claim their foreign funds are otherwise ‘trapped’ abroad, but new data show that is not true," said Sen. Carl Levin, D-Mich., in a press statement. "Many U.S. multinationals have already invested a large portion of their foreign funds right here in the United States, taking full advantage of the safety and security of the U.S. financial system to protect their money while paying no U.S. taxes on those funds to support the U.S. system."

The survey also found that use of offshore tax havens varied widely among corporations. Nine of the 27 companies, including Apple, Cisco, Google and Microsoft, held between 75 and 100 percent of their tax-deferred foreign earnings in U.S. assets.

A one-year tax "holiday" in 2004 cut the corporate tax rate on repatriated funds to 5.25 percent. The amount of money flowing back to the United States jumped, but studies show that the repatriated money did not increase jobs or research expenditures, and instead the companies increased their spending on stock buybacks and executive pay.

"The large cash repatriations that followed from that tax holiday in net terms funded shareholder dividends and stock buybacks, not structural investments in the U.S. real economy," Kleinbard testified to Congress in June, according to CNNMoney.

Former Treasury Secretary Lawrence Summers advocates eliminating the distinction between repatriated and unrepatriated foreign corporate profits

Foreign income should be taxed at a lower, fixed rate of about 15 percent, Summers wrote in a blog for Reuters.

"Such a proposal," he explained, "could easily be designed to raise revenue relative to the current baseline, encourage the repatriation of funds to the United States and reduce the competitive disadvantage faced by U.S. multinationals operating abroad."

Editor's Note: How to Pay Zero Taxes . . . Legally