About two-thirds of corporations operating in the United States did not pay taxes annually from 1998 to 2005, according to a [report] from the U.S. Government Accountability Office. In 2005, after collectively making $2.5 trillion in sales, corporations gave a variety of reasons on their tax returns to account for the absence of taxable revenue. The most frequently listed included the cost of producing their goods, salary expenses and interest payments on their debt, the report said. Sen. Byron L. Dorgan (D-N.D.) called the findings a shocking indictment of the current tax system." "It's shameful that so many corporations make big profits and pay nothing to support our country," he said. "The tax system that allows this wholesale tax avoidance is an embarrassment and unfair to hardworking Americans who pay their fair share of taxes. We need to plug these tax loopholes and put these corporations back on the tax rolls." In 2005, about 28 percent of large corporations paid no taxes. Of the 1.3 million corporations included in the study, 998 were categorized as "large." Dorgan and Sen. Carl M. Levin (D-Mich.) requested the report out of concern that some corporations were using "transfer pricing" to reduce their tax bills. The practice allows multi-national companies to transfer goods and assets between internal divisions so they can record income in a jurisdiction with low tax rates. Levin said: "This report makes clear that too many corporations are using tax trickery to send their profits overseas and avoid paying their fair share in the United States."