For purposes of column I of the table appearing in subsection (a), as that subsection was in effect in December 1977, an individual’s primary insurance benefit shall be computed as follows:

(A) The individual’s average monthly wage shall be determined as provided in subsection (b), as in effect in December 1977 (but without regard to paragraph (4) thereof and subject to section 104(j)(2) of the Social Security Amendments of 1972), except that for purposes of paragraphs (2)(C) and (3) of that subsection (as so in effect) 1936 shall be used instead of 1950.

(B) For purposes of subparagraphs (B) and (C) of subsection (b)(2) (as so in effect)— (i) the total wages prior to 1951 (as defined in subparagraph (C) of this paragraph) of an individual— (I) shall, in the case of an individual who attained age 21 prior to 1950, be divided by the number of years (hereinafter in this subparagraph referred to as the “divisor”) elapsing after the year in which the individual attained age 20, or 1936 if later, and prior to the earlier of the year of death or 1951, except that such divisor shall not include any calendar year entirely included in a period of disability, and in no case shall the divisor be less than one, and (II) shall, in the case of an individual who died before 1950 and before attaining age 21, be divided by the number of years (hereinafter in this subparagraph referred to as the “divisor”) elapsing after the second year prior to the year of death, or 1936 if later, and prior to the year of death, and in no case shall the divisor be less than one; and (ii) the total wages prior to 1951 (as defined in subparagraph (C) of this paragraph) of an individual who either attained age 21 after 1949 or died after 1949 before attaining age 21, shall be divided by the number of years (hereinafter in this subparagraph referred to as the “divisor”) elapsing after 1949 and prior to 1951. The quotient so obtained shall be deemed to be the individual’s wages credited to each of the years which were used in computing the amount of the divisor, except that— (iii) if the quotient exceeds $3,000, only $3,000 shall be deemed to be the individual’s wages for each of the years which were used in computing the amount of the divisor, and the remainder of the individual’s total wages prior to 1951 (I) if less than $3,000, shall be deemed credited to the computation base year (as defined in subsection (b)(2) as in effect in December 1977) immediately preceding the earliest year used in computing the amount of the divisor, or (II) if $3,000 or more, shall be deemed credited, in $3,000 increments, to the computation base year (as so defined) immediately preceding the earliest year used in computing the amount of the divisor and to each of the computation base years (as so defined) consecutively preceding that year, with any remainder less than $3,000 being credited to the computation base year (as so defined) immediately preceding the earliest year to which a full $3,000 increment was credited; and (iv) no more than $42,000 may be taken into account, for purposes of this subparagraph, as total wages after 1936 and prior to 1951.

(C) For the purposes of subparagraph (B), “total wages prior to 1951” with respect to an individual means the sum of (i) remuneration credited to such individual prior to 1951 on the records of the Commissioner of Social Security, (ii) wages deemed paid prior to 1951 to such individual under section 417 of this title , (iii) compensation under the Railroad Retirement Act of 1937 [ 45 U.S.C. 228a et seq.] prior to 1951 creditable to him pursuant to this subchapter, and (iv) wages deemed paid prior to 1951 to such individual under section 431 of this title .

(D) The individual’s primary insurance benefit shall be 40 percent of the first $50 of his average monthly wage as computed under this subsection, plus 10 percent of the next $200 of his average monthly wage, increased by 1 percent for each increment year. The number of increment years is the number, not more than 14 nor less than 4, that is equal to the individual’s total wages prior to 1951 divided by $1,650 (disregarding any fraction).