By David Cay Johnston

The views expressed are his own.

In a competitive market, economists argue endlessly about who bears the burden of corporate income tax. Is it owners, who get a smaller net return? Or workers, who make less? Or suppliers, who get lower prices? Or customers, who pay higher prices?

In one sector of the U.S. economy, however, the answer is clear-cut. Corporate-owned utilities (mostly electric and natural gas) and pipeline partnerships, all of them legal monopolies, pass their income tax burdens on to customers.

Now a study, released last week, provides powerful new evidence that these two industries convert corporate income taxes from a burden to a benefit.

The study was prepared by Citizens for Tax Justice and the Institute on Taxation and Economic Policy. Both are foundation-backed nonprofits that say the tax system favors the rich and corporations over most Americans.

Utilities charge prices, known as rates, set by political appointees who regulate the industry. Embedded in those rates are generous sums to cover corporate income and all other taxes. Pacific Gas & Electric, the northern California utility, was awarded $431 million to pay 2007 corporate income taxes, a final decision by the California Public Utilities Commission shows. Similar amounts were approved, or are in the process of final approval, for each subsequent year.