According to a study released today, 30 of the biggest publicly traded American companies paid “less than zero” in taxes in the last three years, and 78 companies didn’t pay any federal income tax in at least one of those years, MSNBC reported. Only 71 of the 280 companies, or about 25 percent, paid more than 30 percent in taxes over the last three years.

The study, conducted by liberal tax research groups Citizens for Tax Justice and the Institute on Taxation and Economic Policy, examined the corporate filings of 280 companies in the Fortune 500 that were profitable for all three years between 2008 and 2010, CNN Money reported.

The average tax rate of all 280 companies during that period was 18.5 percent, the researchers found. That’s about half the official corporate rate of 35 percent and less than big companies in many industrialized nations pay, the New York Times observed.

Tax breaks ranging from special rules on equipment depreciation to industry-specific incentives lowered the companies’ income tax bills.

"Today corporate tax loopholes are so out of control that most Americans can rightfully complain, ‘I pay more federal income taxes than General Electric, Boeing, DuPont, Wells Fargo, Verizon, etc., etc., all put together,” the study’s authors wrote.

According to the New York Times:

The report is being released as corporations are pushing for a cut in their official tax rate, saying the current system puts American companies at a disadvantage with competitors abroad and encourages them to shift jobs and investments overseas. The Congressional supercommittee charged with cutting the budget deficit is also considering proposals to revamp the tax system, simplifying the corporate structure and possibly lowering corporate rates.

Among the companies that paid less than zero in income tax over the three-year period: Pepco Holdings, General Electric, Boeing and Ryder System.

Boeing officials told the New York Times that the company had paid some federal taxes, but declined to elaborate. The company said it benefited from tax breaks intended to encourage hiring.

GE called the study "inaccurate and distorted,” CNN Money reported. In a statement, the company said: "GE paid billions of dollars in taxes in the United States over the last decade, and we expect our overall tax rate will be approximately 30 percent in 2011. We believe the U.S. tax system needs to be reformed to close all loopholes, to lower the corporate rate and to provide a territorial system like every other major country in the world."