Social Security Disability Insurance (SSDI) and Veterans Disability Compensation (VDC)--administered by the Social Security Administration (SSA) and the Department of Veterans Affairs (VA) respectively--are two of the largest federal disability programs, but strongly differ along several dimensions, including the populations served, how each program defines a "disability," as well as varying eligibility requirements. First, SSDI is an insurance program that replaces a portion of earnings for an eligible worker whose illness or injury--while not necessarily caused by a work-related incident--results in an inability to work. SSDI is one of several federal programs funded through the Federal Insurance Contributions Act (FICA) payroll tax and the Self-Employment Contributions Act (SECA) tax to which all workers and employers in covered occupations (including military personnel) and self- employed individuals make contributions. On the other hand, VDC is not insurance, but is a compensation program in that payments are made to veterans who develop medical conditions that are related to their service in the military. VDC is non-contributory and neither veterans nor active military personnel pay into the program, which is funded through a mandatory appropriation as part of the VA annual budget. Second, while the purpose of both SSDI and VDC is to provide ...