What is the test for being disabled for purposes of social security disability?

A claimant is disabled for purposes of social security disability benefits if he can establish that a medically determinable physical or mental impairment prevents him from engaging in substantial gainful activity, and the impairment is expected to result in death or to last for a continuous one year period. See 42 U.S.C. 423(d)(1)(A) (Supp.1997); see Swenson v. Sullivan, 876 F.2d 683, 687 (9th Cir.1989). For purposes of 42 U.S.C. 423(d)(1)(A), a claimant is unable to engage in substantial gainful activity if he cannot perform his previous occupational duties and, given his age, education, and work experience, cannot engage in any other kind of substantial gainful work which exists in the national economy. See 42 U.S.C. 423(d)(2)(A)