What is the difference between disability benefits and Social Security Disability benefits?

SSI benefits are based on needs. To be eligible, a claimant must be "aged, blind or disabled," and must have income and resources under certain thresholds. See id. 1382(a). In contrast, SSDI benefits are based on earnings. The claimant must be disabled, and must have contributed to a federal insurance trust fund through deductions in his or her wages. See id. 401(b) ; see generally Bowen v. Galbreath , 485 U.S. 74, 75, 108 S.Ct. 892, 99 L.Ed.2d 68 (1988). Unlike SSI benefits, SSDI benefits are limited to a certain period of insurance. The length of this insured period is determined by the amount of the claimant's previously taxed earnings. See 42 U.S.C. 423(c)(1). The definition of "disability" for SSI benefits is the same as for SSDI benefits. Compare 42 U.S.C. 423(d)(1)(A) (Title II), with id. 1382c(a)(3)(A) (Title XVI).