America's $4.6 trillion retirement hole

NEW YORK (CNNMoney.com) -- Americans are woefully unprepared to pay for retirement, according to research released Thursday.

On average, U.S. workers would need to have an additional $48,000 when they retire at 65 to ensure they don't run shy of cash in retirement, the Employee Benefit Research Institute said.

All told, the group estimates that the national retirement deficit is $4.6 trillion.

The research group estimated how much money retirees will need for "basic" expenses such as food, shelter and uninsured health care costs. It compared those expenses to the financial resources workers are likely to have at the typical retirement age, including Social Security, pensions and savings plans such as 401(k)s.

If Social Security benefits are deducted, the group estimates that the national retirement deficit would jump to $8.5 trillion, or about $89,000 for the average worker.

In all cases, low-income workers are most at risk of not having enough savings to retire on, Jack VanDerhei, research director at EBRI, told lawmakers Thursday. EBRI estimates that 41% of low-income Baby Boomers will run short of money within 10 years of retirement.

However, he noted that the number of households that are projected to have inadequate retirement income has declined since the last time EBRI studied the topic in 2003.

VanDerhei said the improvement over the last seven years is largely due to an increase in the number of employers that automatically enroll workers in 401(k) plans.

Automatic enrollment, which allows workers to opt out, can increase participation in retirement savings plans dramatically, he said, particularly among lower-income employees.