What is the burden of proving an applicant has performed or substantially gainful employment that exists in the national economy?

performed or any other substantially gainful employment that exists in the national economy. See 42 U.S.C. 423(d)(1)(A), (2)(A). An applicant must meet both requirements to be "disabled." Id. Further, the applicant bears the burden of proving he or she was either permanently disabled or subject to a condition which became so severe as to disable the applicant prior to the date upon which his or her disability insured status expired. Johnson v. Shalala, 60 F.3d 1428, 1432 (9th Cir. 1995).