What is a disability under the Social Security Act?

Under the Social Security Act, a "disability" is an "inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months." 42 U.S.C. 423(d)(1)(A). To determine whether an individual is disabled, the Commissioner employs a five-step sequential evaluation process. See 20 C.F.R. 404.1520. Until the final step in this process, the burdens of production and persuasion remain solely with the claimant. See Balsamo v. Chater, 142 F.3d 75, 80 (2d Cir. 1998).