About 46.2 million people remained below the poverty line in 2011, according to a report by the U.S. Census Bureau. The number is unchanged from 2010 and is the highest in more than half a century.

Poverty is greatest among children (21.9 percent), compared with seniors (8.7 percent) and working-age adults (13.7 percent).

For the second consecutive year,  the median annual household income declined to $50,054, down 1.5 percent from 2010.

Researchers at the West Coast Poverty Center at the University of Washington note that the data released by the Census Bureau is just one way of measuring economic need. Because it relies on an outdated formula to determine the minimum income needed to survive, the poverty rate likely underestimates the number of impoverished Americans, the researchers said.

In 2011, a family of two working-age adults and two children was considered poor if its annual income fell below $22,811. But the poverty line does not take into account issues like geographic variation in the cost of living or the value of government benefits like food stamps.

"The poverty rate is useful for comparing trends over time, but it doesn't do a good job of setting a bar for how much money families need to get by," said Jennifer Romich, director of the West Coast Poverty Center and an associate professor at the UW School of Social Work. "In spite of its imperfections, what the poverty measure does tell us is that over 46 million people are living with incomes below a very low threshold."

The report showed that the number of Hispanics in poverty in the United States dropped by 1.2 percent from 2010 to 2011. Overall, 25 percent of Latinos remain stuck among America's poorest.

The number of Latinos in poverty fell from 13,522,000 to 13,244,000. Whites saw a 0.1 percent increase in poverty rates and black and Asians saw a 0.2 percent increase. 

The median household income for Hispanics dropped 0.5 percent from $38,818 to $38,624 - the smallest drop of any group.

New Mexico had the highest share of poor people, at 22.2 percent followed by Louisiana, the District of Columbia, South Carolina, Arkansas and Georgia. 

The share of Americans without health coverage fell from 16.3 percent to 15.7 percent, or 48.6 million people. It was the biggest decline in the number of uninsured since 1999, boosted in part by increased coverage for young adults under the new health care law that allows them to be covered under their parents' health insurance until age 26.

The Census Bureau will release more accurate state-level estimates and estimates for large cities and counties on Sept. 20, followed by a report in November that will include a more complete picture of income, expenses and the cost of living.