The number of working Americans earning so little they lived in poverty reached 7.2 per cent of the labor force in 2010, the highest level in at least two decades, the US government said on Friday.

The Bureau of Labor Statistics counted 7.6 per cent of women among the working poor, compared to 6.7 per cent of men. In 2009, the working poor rate was 7 per cent.

Education made a huge difference. Among workers who had not graduated from high school, 21.4 per cent lived below the official poverty line against only 2.1 per cent of those with a university degree.

The highest rate was amongst the unemployed looking for work during the year at 35.1 per cent.

The official poverty line in 2010 was an annual income of $10,830 for a single person and $22,050 for a family of four.

Overall, the United States had 46.2 million people living in poverty that year, or 15.1 per cent of the population of all ages. The working poor totaled 10.5 million.

The Bureau of Labor Statistics conducted a special survey in 2011 which it is used to calculate the figures, based on those who were in the labor force for at least 27 weeks either working or looking for work.

The rate for working poor was 5.5 per cent in 1987, the furthest back that the BLS included in its report, and in 1999 it fell below 5 per cent.-Reuters