While overall poverty levels are low by historical standards, the increase in poverty this year has been swift. It is the biggest jump in a single year since the government began tracking poverty 60 years ago. It is nearly double the next-largest rise, which occurred in 1979-1980 during the oil crisis, according to James X. Sullivan, a professor at Notre Dame, and Bruce D. Meyer, a professor at the University of Chicago’s Harris School of Public Policy.

Sullivan and Meyer created a Covid-19 Income and Poverty Dashboard to track how many Americans are falling below the poverty line during this deep recession. The federal poverty line is $26,200 for a family of four.

The economists say the sharp rise in poverty is occurring for two reasons: Millions of people cannot find jobs, and government aid for the unemployed has declined sharply since the summer. The average unemployment payment was more than $900 a week from late March through the end of July, but it fell to about $300 a week in August, making it harder for the unemployed to pay their bills.