The bureau’s findings were worse than many economists expected, and brought into sharp relief the toll the past decade — including the painful declines of the financial crisis and recession —had taken on Americans at the middle and lower parts of the income ladder. It is also fresh evidence that the disappointing economic recovery has done nothing for the country’s poorest citizens.

The report said the percentage of Americans living below the poverty line last year, 15.1 percent, was the highest level since 1993. (The poverty line in 2010 for a family of four was $22,314.)

The report comes as President Obama gears up to try to pass a jobs bill, and analysts said the bleak numbers could help him make his case for urgency. But they could also be used against him by Republican opponents seeking to highlight economic shortcomings on his watch.

“This is one more piece of bad news on the economy,” said Ron Haskins, a director of the Center on Children and Families at the Brookings Institution. “This will be another cross to bear by the administration.”

The past decade was also marked by a growing gap between the very top and very bottom of the income ladder. Median household income for the bottom tenth of the income spectrum fell by 12 percent from a peak in 1999, while the top 90th percentile dropped by just 1.5 percent. Overall, median household income adjusted for inflation declined by 2.3 percent in 2010 from the previous year, to $49,445. That was 7 percent less than the peak of $53,252 in 1999. Part of the income decline over time is because of the smaller size of the American family.