More Americans receive disability benefits than 20 years ago though people are less likely to have physically demanding jobs, health care has improved and the Americans With Disabilities Act bans discrimination against the handicapped.

"The weird thing is disability enrollment is going up like crazy" when "we should be able to help keep people in the workforce," Duggan said.

Two Programs

Social Security is comprised of two separate programs: the retirement plan supporting 40 million senior citizens and 6 million survivors, and the disability insurance program created during the Dwight Eisenhower administration to prevent sick and injured workers from becoming destitute.

The disability program currently pays benefits averaging $1,111 a month, with the money coming from the Social Security payroll tax taken out of workers' paychecks.

The program cost $132 billion last year, more than the combined annual budgets of the departments of Agriculture, Homeland Security, Commerce, Labor, Interior and Justice.

That doesn't include an additional $80 billion spent because disability beneficiaries become eligible for Medicare, regardless of their age, after a two-year waiting period.

The disability program, which has been spending more than it receives in revenue for four consecutive years, is projected to exhaust its trust fund in 2016, according to a Social Security trustees report released last month. By comparison, the separate trust fund financing senior citizens' Social Security benefits is projected to run out in 2035 while Medicare's primary fund will be exhausted in 2024.

$600 Billion

The retirement portion of Social Security costs $600 billion a year, while Medicare costs $560 billion annually.

Once the disability program runs through its reserve, incoming payroll-tax revenue will cover only 79 percent of benefits, according to the trustees. Because the plan is barred from running a deficit, aid would have to be cut to match revenue.