More households are at risk of failing to maintain their standard of living during retirement, according to the Center for Retirement Research at Boston College.

The institute today updated its National Retirement Risk Index, a measurement that evaluates American households’ financial assets, housing and changes in Social Security benefits in order to weigh retirement readiness. Nationwide Mutual Insurance Co. underwrites the index.

The latest index shows that 51% of Americans aren’t prepared to retire at 65, up from 44% in 2007, when the index was last updated.

This estimate doesn’t consider the cost of health care or long-term care. If those were included, 70% of the population wouldn’t be prepared to retire, according to Paul Ballew, Nationwide Mutual’s senior vice president of customer insights and analytics.

Results also show that younger households have felt the brunt of the impact of the economic decline.

Fully 56% of households led by Generation Xers are at risk of failing to meet retirement needs, compared with 49% in 2007. The loss of pension plans, as well as troubles with the Social Security system, place younger generations at a higher risk of being unable to hold on to their standards of living during retirement, Mr. Ballew said in an interview.

“The cradle-to-the-grave relationship with the employer is severed,” he said. “Younger people have to be responsible for their own retirement.”

In the aftermath of the crisis, a combination of distrust of advisers and increased interest in “simple assets” and savings vehicles to deal with immediate money shortages may have distracted some households from saving for retirement, Mr. Ballew said.

“There’s a hunker-down mentality,” he said. “Crisis management — dealing with a deficit on the household balance sheet — takes precedence over retirement planning.”