Fraud appears limited to relatively few cases in the disability program, although it is difficult to know precisely how many beneficiaries could be working. A report by the nonpartisan Government Accountability Office found that about 0.4 percent of disability beneficiaries were likely receiving improper payments, because they were working before or after they began receiving checks. Another report by Social Security's inspector general examined administrative law judges who were approving an unusually high proportion of disability applications and concluded that some of those approvals may have been mistaken. That group of beneficiaries also accounted for about 0.4 percent of all those receiving disability payments.

And while it's true that more and more people are on disability, this is largely a result of the fact that the workforce is getting older and more likely to be hurt or sick, according to Kathy Ruffing of the Center on Budget and Policy Priorities, a left-of-center think tank. About seven in ten disability recipients are at least 50 years old -- and that group is also expanding to include the women who entered the workforce at the beginning of their careers decades ago.