20 CFR §404.1511

1. (a)Disabled workers, persons disabled since childhood and, for months after December 1990, disabled widows, widowers, and surviving divorced spouses. If you are entitled to disability cash benefits as a disabled worker, or to child's insurance benefits, or, for monthly benefits payable after December 1990, to widow's, widower's, or surviving divorced spouse's monthly benefits, a disabling impairment is an impairment (or combination of impairments) which, of itself, is so severe that it meets or equals a set of criteria in the Listing of Impairments in appendix 1 of this subpart or which, when considered with your age, education, and work experience, would result in a finding that you are disabled under § 404.1594. In determining whether you have a disabling impairment, earnings are not considered.
2. (b)Disabled widows, widowers, and surviving divorced spouses, for monthly benefits for months prior to January 1991. If you have been entitled to disability benefits as a disabled widow, widower, or surviving divorced spouse and we must decide whether you had a disabling impairment for any time prior to January 1991, a disabling impairment is an impairment (or combination of impairments) which, of itself, was so severe that it met or equaled a set of criteria in the Listing of Impairments in appendix 1 of this subpart, or results in a finding that you were disabled under § 404.1579. In determining whether you had a disabling impairment, earnings are not considered.