Still, at the very moment anti-tax protesters were emerging as the most powerful force in American politics, handing Republicans landslide control of the U.S. House, the data show that people were sending the smallest portion of their income to the federal government since 1979.

During Obama’s first year in office, the average tax rate paid by all households fell to 17.4 percent, down from 19.9 percent in 2007, according to the CBO. The 2009 rate was significantly lower than the previous low of 19.4 percent in 2003 and well below the 30-year average of 21 percent.

The tax burden — which includes all forms of federal levies, including income, payroll and corporate taxes — lightened for households across the board, thanks in part to Obama’s signature “Making Work Pay” tax credit and other tax cuts passed as part of the 2009 economic stimulus package, the CBO said.

The lowest fifth of earners benefited the most, sending just 1 percent of their before-tax income to the federal government in 2009, compared with 5.1 percent in 2007. The top fifth of earners paid 23.2 percent, compared with 24.7 percent in 2007.

The average federal income tax rate also reached a new low, settling at 7.2 percent in 2009 — 2 points lower than in 2007, the CBO said.

Although detailed data are available only through 2009, the CBO said more recent estimates suggest that effective tax rates remained at historically low levels in 2010 and 2011.

“However much Republicans try to perpetuate false claims, the facts speak for themselves: Tax rates have never been lower than under President Obama,” said Rep. Sander M. Levin (Mich.), the senior Democrat on the tax-writing House Ways and Means Committee.

Republicans countered that the low rates won’t last long if Obama wins reelection and follows through on his pledge to let the George W. Bush-era tax cuts expire for the roughly 2 percent of households that make more than $250,000 a year, a group that includes many business owners and investors.

Obama reiterated that pledge Monday, urging lawmakers to act now to extend the Bush tax cuts through 2013 for the vast majority of households. The tax cuts, enacted in 2001 and 2003, are scheduled to expire in January.

“The benefits of lower tax levels have been undercut by the president’s ideological fixation with raising taxes on small businesses,” said Michael Steel, a spokesman for House Speaker John A. Boehner (R-Ohio). “Despite yet another disappointing jobs report on Friday, he doubled down on insisting on that tax hike yesterday.”

White House spokeswoman Amy Brundage took credit for the low tax rates while acknowledging the recession’s broader toll.

“While the President has fought since day one to cut taxes for the middle class by a total of $3,600 a year, Americans are still fighting to make ends meet,” Brundage said by e-mail. “That’s why the President won’t rest until Congress acts to extend the tax rates for the middle class through next year.”