Barnhart V. Thomas

Under the Social Security Act, the Social Security Administration (SSA) is authorized to pay disability insurance benefits and Supplemental Security Income to persons who have a "disability." A person qualifies as disabled, and thereby eligible for such benefits, "only if his physical or mental impairment or impairments are of such severity that he is not only unable to do his previous work but cannot, considering his age, education, and work experience, engage in any other kind of substantial gainful work which exists in the national economy." 42 U. S. C. §§423(d)(2)(A), 1382c(a)(3)(B). The issue we must decide is whether the SSA may determine that a claimant is not disabled because she remains physically and mentally able to do her previous work, without investigating whether that previous work exists in significant numbers in the national economy.