1. Summarize the facts of the case.
2. Who brought the two court actions against Corning Glass Works?
3. Does the statutory term “working conditions” encompass the time of day worked?

MARSHALL, J.…
These cases arise under the Equal Pay Act of 1963, 29 U.S.C. Section 206(d)(1), which added to the Fair Labor Standards Act the principle of equal pay for equal work regardless of sex. The principal question posed is whether Corning Glass Works violated the Act by paying a higher base wage to male night shift inspectors than it paid to female inspectors performing the same tasks on the day shift, where the higher wage was paid in addition to a separate night shift differential paid to all employees for night work. In No. 73-29, the Court of Appeals for the Second Circuit, in a case involving several Corning plants in Corning, New York, held that this practice violated the Act. 474 F.2d 226 (1973). In No. 73-695, the Court of Appeals for the Third Circuit, in a case involving a Corning plant in Wellsboro, Pennsylvania, reached the opposite conclusion. 480 F.2d 1254 (1973). We granted certiorari and consolidated the cases to resolve this unusually direct conflict between two circuits. Finding ourselves in substantial agreement with the analysis of the Second Circuit, we affirm in No. 73-29 and reverse in No. 73-695.
I.
Prior to 1925, Corning operated its plants in Wellsboro and Corning only during the day, and all inspection work was performed by women. Between 1925 and 1930, the company began to introduce automatic production equipment which made it desirable to institute a night shift. During this period, however, both New York and Pennsylvania law prohibited women from working at night. As a result, in order to fill inspector positions on the new night shift, the company had to recruit male employees from among its male day workers. The male employees so transferred demanded and received wages substantially higher than those paid to women inspectors engaged on the two day shifts. During this same period, however, no plantwide shift differential existed and male employees working at night, other than inspectors, received the same wages as their day shift counterparts. Thus a situation developed where the night inspectors were all male, the day inspectors all female, and the male inspectors received significantly higher wages.
In 1944, Corning plants at both locations were organized by a labor union and a collective bargaining agreement was negotiated for all production and maintenance employees. This agreement for the first time established a plantwide shift differential, but this change did not eliminate the higher base wage paid to male night inspectors. Rather, the shift differential was superimposed on the existing differences in base wages between male night inspectors and female day inspectors.
Prior to the June 11, 1964, effective date of the Equal Pay Act, the law in both Pennsylvania and New York was amended to permit women to work at night. It was not until some time after the effective date of the Act, however, that Corning initiated efforts to eliminate the differential rates for male and female inspectors. Beginning in June 1966, Corning started to open up jobs on the night shift to women. Previously separate male and female seniority lists were consolidated and women became eligible to exercise their seniority, on the same basis as men, to bid for the higher paid night inspection jobs as vacancies occurred.
On January 20, 1969, a new collective bargaining agreement went into effect, establishing a new "job evaluation" system for setting wage rates. The new agreement abolished for the future the separate base wages for day and night shift inspectors and imposed a uniform base wage for inspectors exceeding the wage rate for the night shift previously in effect. All inspectors hired after January 20, 1969, were to receive the same base wage, whatever their sex or shift. The collective bargaining agreement further provided, however, for a higher "red circle" rate for employees hired prior to January 20, 1969, when working as inspectors on the night shift. This "red circle" rate served essentially to perpetuate the differential in base wages between day and night inspectors.
The Secretary of Labor brought these cases to enjoin Corning from violating the Equal Pay Act and to collect back wages allegedly due female employees because of past violations. Three distinct questions are presented: (1) Did Corning ever violate the Equal Pay Act by paying male night shift inspectors more than female day shift inspectors? (2) If so, did Corning cure its violation of the Act in 1966 by permitting women to work as night shift inspectors? (3) Finally, if the violation was not remedied in 1966, did Corning cure its violation in 1969 by equalizing day and night inspector wage rates but establishing higher "red circle" rates for existing employees working on the night shift?
II.
Congress' purpose in enacting the Equal Pay Act was to remedy what was perceived to be a serious and endemic problem of employment discrimination in private industry-the fact that the wage structure of "many segments of American industry has been based on an ancient but outmoded belief that a man, because of his role in society, should be paid more than a woman, even though his duties are the same." S. Rept. No. 176, 88th Cong., 1st Sess. (1963), at 1. The solution adopted was quite simple in principle: to require that "equal work be rewarded by equal wages." Ibid.
The Act's basic structure and operation are similarly straightforward. In order to make out a case under the Act, the Secretary must show that an employer pays different wages to employees of opposite sexes "for equal work on jobs the performance of which requires equal skill, effort, and responsibility, and which are performed under similar working conditions." Although the Act is silent on this point, its legislative history makes plain that the Secretary has the burden of proof on this issue, as both of the courts below recognized.