WASHINGTON - More than one in five Americans saw their available household income decline by a quarter or more in the past three years, according to a report released Monday.

They also lacked an adequate financial cushion to cope with this decline, which together with the 25 percent or more decrease of income, constitutes the major factors of economic insecurity, said the report.

The report updated an Economic Security Index (ESI) developed by Jacob Hacker, a political science professor at Yale University.

A record 20.5 percent of the American people faced this situation in the most recent economic downturn, a sharp increase from 14.3 percent in 1986. Roughly 62 million Americans were insecure in 2010, indicated the Index.

While economic insecurity increased across the country, the ESI found some groups suffered more than others in the past three years, such as those living in the West and the South more disadvantaged than those in the Northeast and North Central part of the country.

And levels of insecurity were much higher among those with limited education, as well as among racial minorities and younger workers.

The ESI is likely to remain high in the coming years, given continuing economic distress, said the report, adding that the economic security of Americans is under greater threat today than at any point over the last 25 years.

The novel ESI serves as another economic indicator, complementing unemployment and poverty rates to reflect the dynamic American financial well-being.