Under § 215 of the Social Security Act, as added, 64 Stat. 506, and amended, 42 U. S. C. § 415 (1970 ed. and Supp. V), old-age insurance benefits are computed on the basis of the wage earner’s “average monthly wage” earned during his “benefit computation years” which are the “elapsed years” (reduced by five) during which the wage earner’s covered wages were highest. Until a 1972 amendment, “elapsed years” depended upon the sex of the wage earner. Section 215 (b) (3) prescribed that the number of “elapsed years” for a male wage earner would be three higher than for an otherwise similarly situated female wage earner; for a male, the number of “elapsed years” equaled the number of years that elapsed after 1950 and before the year in which he attained age 65; for a female the number of “elapsed years” equaled the number of years that elapsed after 1950 and before the year in which she attained age 62.1 Thus, a male born in 1900 *315would have 14 “elapsed years” on retirement at age 65 but a female born in the same year would have only 11.2 Accordingly, a female wage earner could exclude from the computa*316tion of her “average monthly wage” three more lower earning years than a similarly situated male wage earner could exclude. This would result in a slightly higher “average monthly wage” and a correspondingly higher level of monthly old-age benefits for the retired female wage earner.3 A single-judge District Court for the Eastern District of New York, on review under § 205 (g) of the Social Security Act, 42 U. S. C. § 405 (g), of a denial, after hearing, of appellee’s request that the more favorable formula be used to compute his benefits, held that, on two grounds, the statutory scheme violated the equal protection component of the Due Process Clause of the Fifth Amendment: (1) that to give women who reached age 62 before 1975 greater benefits than men of the same age and earnings record was irrational,4 and (2) that in any event the 1972 amendment was to be construed to apply retroactively, because construing the amendment to give men who reach age 62 in 1975 or later the benefit of the 1972 amendments but to deny older men the same benefit would render the amendment irrational, and therefore unconstitutional. 413 F. Supp. 127 (1976). We reverse.

To withstand scrutiny under the equal protection component of the Fifth Amendment’s Due Process Clause, “classifications *317by gender must serve important governmental objectives and must be substantially related to achievement of those objectives.” Craig v. Boren, 429 U. S. 190, 197 (1976). Reduction of the disparity in economic condition between men and women caused by the long history of discrimination against women has been recognized as such an important governmental objective. Schlesinger v. Ballard, 419 U. S. 498 (1975); Kahn v. Shevin, 416 U. S. 351 (1974). But “the mere recitation of a benign, compensatory purpose is not an automatic shield which protects against any inquiry into the actual purposes underlying a statutory scheme.” Weinberger v. Wiesenfeld, 420 U. S. 636, 648 (1975). Accordingly, we have rejected attempts to justify gender classifications as compensation for past discrimination against women when the classifications in fact penalized women wage earners, Califano v. Goldfarb, ante, at 209 n. 8; Weinberger v. Wiesenfeld, supra, at 645, or when the statutory structure and its legislative history revealed that the classification was not enacted as compensation for past discrimination. Califano v. Goldfarb, ante, at 212-216 (plurality opinion), 221-222 (Stevens, J., concurring in judgment); Weinberger v. Wiesenfeld, supra, at 648.

The statutory scheme involved here is more analogous to those upheld in Kahn and Ballard than to those struck down in Wiesenfeld and Goldfarb. The more favorable treatment of the female wage earner enacted here was not a result of “archaic and overbroad generalizations” about women, Schlesinger v. Ballard, supra, at 508, or of “the role-typing society has long imposed” upon women, Stanton v. Stanton, 421 U. S. 7, 15 (1975), such as casual assumptions that women are “the weaker sex” or are more likely to be child-rearers or dependents. Cf. Califano v. Goldfarb, supra; Weinberger v. Wiesenfeld, supra. Rather, “the only discernible purpose of [§ 215’s more favorable treatment is] the permissible one of redressing our society’s longstanding disparate treatment of women.” Califano v. Goldfarb, ante, at 209 n. 8.

*318The challenged statute operated directly to compensate women for past economic discrimination. Retirement benefits under the Act are based on past earnings. But as we have recognized: “Whether from overt discrimination or from the socialization process of a male-dominated culture, the job market is inhospitable to the woman seeking any but the lowest paid jobs.” Kahn v. Shevin, 416 U. S., at 353. See generally id., at 353-354, and nn. 4-6. Thus, allowing women, who as such have been unfairly hindered from earning as much as men, to eliminate additional low-earning years from the calculation of their retirement benefits works directly to remedy some part of the effect of past discrimination.5 Cf. Schlesinger v. Ballard, supra, at 508.

The legislative history of § 215 (b) (3) also reveals that Congress directly addressed the justification for differing treatment of men and women in the former version of that section and purposely enacted the more favorable treatment for female wage earners to compensate for past employment discrimination against women. Before 1956, the sexes were treated equally by § 215 (b) (3); the computation it required turned on the attainment of “retirement age,” which was then defined in 42 U. S. C. § 416 (a) (1952 ed.) as 65 for both sexes.6 In 1956, however, retirement age was redefined as 62 for women and 65 for men, Social Security Amendments of *3191956, § 102 (a), 70 Stat. 809, thereby changing the calculation under § 215 (b) (3). A House Report emphasizes that this reduction in the retirement age for women was purposely made to remedy discrimination against women in the job market:

“Your committee believes that the age of eligibility should be reduced to 62 for women workers. . . . A recent study by the United States Employment Service in the Department of Labor showed that age limits are applied more frequently to job openings for women than for men and that the age limits applied are lower.” H. R. Rep. No. 1189, 84th Cong., 1st Sess., 7 (1955).7

The effect of this change on § 215 (b) (3) was also discussed in connection with the amendment of that section in 1961.8 Social Security Amendments of 1961, § 102 (d) (2), 75 Stat. 135. During the hearings on that amendment Representative Watts asked why a woman would draw more benefits than a similarly situated man. After it was noted that this did not change the law as it had existed since 1956, Representative Boggs confirmed that the difference in treatment was not inadvertent:

“If I may interrupt, I think we went into this at great length some years ago when we adopted the 62-year provision for women and the theory was that a woman at that age was less apt to have employment opportunities than a man and despite the fact of some statistics to the effect *320that women live longer than men, I think the other fact is equally commanding, so there is some justification for a distinction between men and women.” Executive Hearings on Social Security Amendments of 1961, before the House Committee on Ways and Means, 87th Cong., 1st Sess., 146-147 (1961).

Thus, the legislative history is clear that the differing treatment of men and women in former § 215 (b) (3) was not “the accidental byproduct of a traditional way of thinking about females,” Califano v. Goldfarb, ante, at 223 (Stevens, J., concurring in judgment), but rather was deliberately enacted to compensate for particular economic disabilities suffered by women.

That Congress changed its mind in 1972 and equalized the treatment of men and women does not, as the District Court concluded, constitute an admission by Congress that its previous policy was invidiously discriminatory. 413 F. Supp., at 129. Congress has in recent years legislated directly upon the subject of unequal treatment of women in the job market.9 Congress may well have decided that “[t]hese congressional reforms . . . have lessened the economic justification for the more favorable benefit computation formula in § 215 (b) (3).” Kohr v. Weinberger, 378 F. Supp. 1299, 1305 (ED Pa. 1974), vacated on other grounds, 422 U. S. 1050 (1975). Moreover, elimination of the more favorable benefit computation for women wage earners, even in the remedial context, is wholly consistent with those reforms, which require equal treatment of men and women in preference to the attitudes of “romantic paternalism” that have contributed to the “long and unfortunate history of sex discrimination.” Frontiero v. Richardson, 411 U. S. 677, 684 (1973).

Finally, there is no merit in appellee’s argument that the failure to make the 1972 amendment retroactive constitutes *321discrimination on the basis of date of birth. Old-age benefit payments are not constitutionally immunized against alterations of this kind. Flemming v. Nestor, 363 U. S. 603 (1960). Congress expressly reserved “[t]he right to alter, amend, or repeal any provision” of the Act, 42 U. S. C. § 1304, and the Fifth Amendment “does not forbid . . . statutory changes to have a beginning and thus to discriminate between the rights of an earlier and later time.” Sperry & Hutchinson Co. v. Rhodes, 220 U. S. 502, 505 (1911). It follows that Congress may replace one constitutional computation formula with another and make the new formula prospective only.

Reversed.

join, concurring in the judgment.

While I am happy to concur in the Court’s judgment, I find it somewhat difficult to distinguish the Social Security provision upheld here from that struck down so recently in Califano v. Goldfarb, ante, p. 199. Although the distinction drawn by the Court between this case and Goldfarb is not totally lacking in substance, I question whether certainty in the law is promoted by hinging the validity of important statutory schemes on whether five Justices view them to be more akin to the “offensive” provisions struck down in Weinberger v. Wiesenfeld, 420 U. S. 636 (1975), and Frontiero v. Richardson, 411 U. S. 677 (1973), or more like the “benign” provisions upheld in Schlesinger v. Ballard, 419 U. S. 498 (1975), and Kahn v. Shevin, 416 U. S. 351 (1974). I therefore concur in the judgment of the Court for reasons stated by Mr. Justice Rehnquist in his dissenting opinion in Goldfarb, in which Mr. Justice Stewart, Mr. Justice Blackmun, and I joined.