New figures have been released by the US census bureau revealing a yearly decline in median household income for Americans, growing inequality and more than one in five children under 18 years old living in poverty.

In a survey of data for 2011, the census discovered that real median household income in the US had dipped by 1.5% from its level in 2010 to sit at $50,054 a year. The fall is the second consecutive annual drop and comes in the middle of a bitterly contested election in which America's tepid economic performance has been a central theme.

While President Barack Obama has based his campaign on a claim to have saved America from the brink of financial disaster, Republican challenger Mitt Romney has lambasted the country's lacklustre economic performance, especially continuing high levels of joblessness.

The figures released by the census also show that little dent has been made on America's high levels of poverty, with some 15% of the nation – representing around 46.2 million people – living in poverty in 2011. The figures are worse for the very young, where the poverty rate for those under the age of 18 is 21.9% – or some 16.1 million children. These latter figures are roughly unchanged in 2011 from 2010.

However, income inequality in the US has grown. The Gini Index, which measures income inequality, increased by 1.6% to a score of 0.477 in 2011. Though few other countries have yet produced figures for 2011, that number for the US shows a more unequal economy for America than the 2010 figures for countries like Uruguay, Argentina and Bangladesh. Within the figures there was also an increase in the share of aggregate income for the top 20% of Americans of 1.6% and – within that group – the top 5% saw a jump of 4.9%.