WINTER, Circuit Judge:
In a previous appeal, Rock v. Norfolk and Western Railway Company, 473 F.2d 1344 (4 Cir.), cert. denied, 412 U.S. 993, 93 S.Ct. 2754, 37 L.Ed.2d 161 (1973), we affirmed the district court’s conclusion that the railroad (N & W) and the unions had engaged in hiring practices illegal under the Civil Rights Act of 1964, 42 U.S.C. §§ 2000e et seq., at the mostly black Barney Yard and the mostly white CT Yard in Norfolk, Virginia. We remanded the case, however, with directions to the district court (a) to prepare a plan for merger of the seniority rosters of each of the yards into a single seniority roster, (b) to consider defendants’ liability for back pay, and (c) to make an allowance for attorneys fees. On remand, plaintiffs sought to raise, as an additional issue, the contention that minimum wage guarantees made to certain N & W employees when Nickel Plate Railroad was merged with N & W should be extended to them.
The district court declined to consider an upward adjustment of plaintiffs’ monthly guarantees by reason of the Nickel Plate merger plan on the ground that since the claim was not asserted until final argument of the case on remand, the assertion was untimely. It ruled that plaintiffs were not entitled to .back pay and it formulated a plan for merging seniority rosters.1 Plaintiffs appeal a second time, challenging the correctness of the denial of back pay, the merger of the seniority rosters for conductors, and the refusal to give effect to the Nickel Plate merger agreements. We find merit in plaintiffs’ several assertions of error, and therefore we vacate the judgment in the respects it is challenged and remand the case for further proceedings.
I.
Because of the full statement of facts in the appeal previously reported, we proceed directly to the legal issues, reciting only such additional facts as are necessary for their full understanding. We consider first plaintiffs’ claim to back pay.
Discrimination in hiring and employment practices has already been established in this case. Under the rule of Albemarle Paper Co. v. Moody, 422 U.S. 405, 95 S.Ct. 2362, 45 L.Ed.2d 280 (1975):
[Gjiven a finding of unlawful discrimination, backpay should be denied only for reasons which, if applied generally, would . not frustrate the central statutory purposes of eradicating discrimination throughout the economy and making persons whole for injuries suffered through past discrimination. (Footnote omitted.) 422 U.S. at 421, 95 S.Ct. at 2373.
See also Robinson v. Lorillard Corp., 444 F.2d 791, 803-04 (4 Cir.), cert. dismissed, 404 U.S. 1006, 92 S.Ct. 573, 30 L.Ed.2d 655 (1971).
The district court advanced four reasons for denying back pay. They were: (a) that the rate of pay for each classification at the Barney and CT Yards was identical; (b) in 1968, N & W offered to dovetail the rosters of the two yards, but this offer was refused by the unions and must have been known and acquiesced in by plaintiffs; (c) while promotions to higher paying positions came more slowly to Barney Yard employees than to CT Yard employees, the disparity resulted from objective employment needs and personal choice on the part of Barney Yard employees; and (d) the two yards are separate and distinct.
With the possible exception of extension of the N & W minimum wage guarantees, we think that a general application of any or all of the district court’s reasons for denying back pay would frustrate the eradication of discrimination and would prevent the victims of discrimination from being made whole for their injuries. Therefore, we think back pay must be awarded.
Although rates of pay at the Barney and CT Yards are identical, it is total income, not rate of pay, by which discrimi[340]*340nation in compensation is measured. Rate of pay is only part of the equation which produces total income. The record reflects that there was significantly less opportunity for work and for promotion, and significantly greater possibility of layoff at Barney than that at the CT Yard. Such opportunities and possibilities are among the “terms and conditions” of employment. When they are unequal and one racially identifiable group is favored over another, racial discrimination in fact has been practiced.
That no Barney Yard men applied for CT Yard jobs does not disprove discrimination or foreclose the back pay remedy. Since Barney Yard men had no seniority rights to exercise in applying or bidding for CT Yard jobs, 473 F.2d at 1346, a Barney Yard employee would be required to forfeit his accumulated seniority in order to obtain employment at the CT Yard. A refusal to commit seniority suicide is not an acceptable reason to deny back pay. Victims of discrimination should not be required to forfeit wage and security benefits accruing because of their seniority in order to remain eligible for purely speculative future back pay relief. A general rule requiring such action would frustrate the central purposes of Title VII.
Even if N & W did offer to dovetail seniority rosters in 1968, the fact is that dovetailing was not accomplished. .Mere bona fides on the part of an employer, not translated into an actual eradication of discrimination, provides no defense to a claim for back pay. Albemarle Paper Co., 422 U.S. at 422, 95 S.Ct. 2362; Griggs v. Duke Power Co., 401 U.S. 424, 432, 91 S.Ct. 849, 28 L.Ed.2d 158 (1971). In any event, the record does not support the district court’s suggestion that plaintiffs knew of the merger offer in 1968. There was affirmative testimony by representatives of the affected class that they had neither seen nor heard of the offer, and a union official testified that it had not been communicated to the black union or its officers. Under Albemarle Paper Co., this purported justification is not a good defense.
The district court found that the disparate promotion rate between the two yards did not justify the back pay remedy. But as a result of “nepotistic” hiring practices, mostly blacks were hired at Barney and mostly whites at CT, and the system of seniority tended to lock blacks into Barney. See 473 F.2d at 1346. In light of the racial pattern of employment at the two yards, the disparate promotion rate, regardless of the identity in pay rates for identical classifications at the yards, made employment at the Barney Yard unlawfully discriminatory.
Nor does the record support the explanation that black Barney employees did not seek promotion and remained at the Barney Yard as a matter of personal preference. The evidence shows that a substantial group of Barney employees accepted promotions at Barney Yard when vacancies occurred. More significantly, the record fails to show that any Barney Yard employee declined a promotion at Barney Yard when an opportunity for promotion arose. Because successful bidding on a job at CT Yard by a Barney Yard employee inevitably meant a loss of seniority, the failure to make such a bid by a Barney Yard employee could hardly be treated as a considered choice. In short, we see no reason to conclude that, if the promotion opportunities open to CT Yard men had been fairly available to Barney Yard men, the latter would have failed to take advantage of them.
Although the two yards are indeed separate and distinct operations, this fact is irrelevant to the back pay issue. At each yard the same general work is performed and both have the same job classifications, employment qualifications, and rates of pay. But because they are racially identifiable and less attractive employment opportunities are presented at the mostly black Barney Yard, there is unlawful discrimination warranting an award of back pay.
Of course we do not decide that each Barney employee is necessarily entitled to an award of back pay. The statistical evidence in the record tended to prove that certain Barney Yard employees fared better [341]*341economically than their counterparts at CT Yard, and other Barney Yard employees, worse.
We approve the approach to the back pay computation developed in Johnson v. Goodyear Tire & Rubber Co., 491 F.2d 1364, 1379-80 (5 Cir. 1974); Pettway v. American Cast Iron Pipe Co., 494 F.2d 211, 259-63 (5 Cir. 1974); and Baxter v. Savannah Sugar Refining Corp., 495 F.2d 437, 443—45 (5 Cir.), cert. denied, 419 U.S. 1033, 95 S.Ct. 515, 42 L.Ed.2d 308 (1974). These cases hold that to justify an award plaintiffs must prove that there is a class whose members suffered economic loss as a result of discrimination. Such proof would establish a prima facie claim to back pay for each member of the class.
The objective of an award of back pay is “to make persons whole for injuries suffered on account of unlawful employment discrimination.” Albemarle Paper Co., 422 U.S. at 418, 95 S.Ct. at 2372. In the case at bar, therefore, the district court must calculate the economic consequences of hypothetical employment at the CT Yard, compare it with the economic consequences of actual employment at the Barney Yard and, if the economic consequences of hypothetical employment are larger than the economic consequences of actual employment, award the difference to the affected class member. To that end, each employee claiming entitlement to an award must establish his identity as a member of the class and must prove both his income during the years of discriminatory employment and the nature of his job. While much of this proof has already been adduced, plaintiffs should have the right to supplement it on remand, if they wish. The employer then should be afforded the opportunity to present proof that any particular class member is not entitled to back pay, for whatever reason: e. g., lack of qualification, free and voluntary decision to fore-go higher-paying work opportunities, lack of higher-paying work opportunities, and the like. If the employer establishes his defense by a preponderance of the evidence, then the member’s prima facie case will be overcome and he should be denied back pay, or have his claim reduced, as the case may be. Otherwise, an award should be made in the amount that the proof establishes.
Some additional comments with respect to the award of back pay are required. N & W argues that because its good faith efforts to dovetail seniority rosters in 1968 were frustrated by the unions, any award of back pay should be assessed solely against the unions. The unions, on the other hand, argue vigorously that any back pay award should be solely against N & W and not against them, even in part.
We do not think that N & W can escape liability to plaintiffs for back pay. As we have said, irrespective of any good faith effort on the part of N & W to obviate the discriminatory effect of separate seniority lists in 1968, the fact is that the discrimination was not obviated; under Albemarle Paper Co., N & W’s good faith efforts cannot insulate it from plaintiffs’ claims. At the same time, 42 U.S.C. § 2000e-5(g) authorizes an award of back pay against an “employer, employment agency, or labor organization, as the case may be, responsible for the unlawful employment practice . .” It may well be that the unions should bear part of any back pay award.2 As between N & W and the unions, Albe-[342]*342marie Paper Co. would not render a good faith effort by N & W to eliminate discrimination irrelevant to the question of which should bear what share of a back pay award. At the same time, consistent with the purposes of the Act, any judgment should be against N & W and the unions jointly and severally, or against N & W solely, with a right to partial indemnity from the unions so as to insure that there be an economic incentive for an employer to obviate discrimination voluntarily, rather than by court decree, and that an employee entitled to back pay shall be made whole by obtaining a judgment against a financially responsible party.
But, the question of whether the unions should bear part of the award for back pay is not ripe for adjudication. It has not yet been decided by the district court. The district court did not reach the issue since it erroneously concluded not to award back pay. Even if we assume that all of the proof relevant to the equitable considerations of a possible division of a back pay award has been adduced, the fact-finding function and the exercise of discretion are vested in the first instance in the district court. We defer to it for initial decision of this issue. We state only that the decision of whether either or both of the unions is to share in N & W’s liability for back pay depends upon whether they combined with N & W to deprive black employees of income opportunities. Carey v. Greyhound, Inc., 500 F.2d 1372, 1379 (5 Cir. 1974); Guerra v. Manchester Terminal Corp., 498 F.2d 641, 655-56 (5 Cir. 1974); Johnson v. Goodyear Tire & Rubber Co., 491 F.2d at 1381-82.
II.
Our mandate with respect to seniority in the earlier appeal was that seniority rosters in the two yards be merged. We directed that with respect to the right of Barney Yard brakemen to qualify for promotion to conductors, “any decree should, while protecting Barney Yard brakemen from prejudice in connection with promotion to this higher classification, not give such brakemen any higher or broader rights than those enjoyed or granted to CT Yard brakemen, who had qualified for promotion to conductors.” 473 F.2d at 1349.
In formulating a decree, the district court merged the two seniority lists and ranked conductor seniority on the basis of date of promotion to conductor. Only the merger of the lists with respect to conductors is questioned in this appeal. Plaintiffs contend that the merger effected by the district court preserves discrimination heretofore practiced with respect to two classes of conductors or potential conductors, i. e., Barney Yard brakemen hired before March 18, 1956, who have been promoted to conductor, and Barney Yard brakemen hired between March 18, 1956 and September 18, 1963 (the date by which every CT Yard brakeman had had an opportunity to be promoted to conductor), who have never had an opportunity to qualify as a conductor.
Plaintiffs contend that merger of the seniority lists with respect to these two classes of conductors and potential conductors should be on the basis of company seniority (date of hire as brakemen) where competition between Barney Yard conduc[343]*343tors (both present and future) and CT Yard conductors is concerned, but that date of qualification as conductor should determine relative seniority among Barney Yard conductors (both present and future), on the one hand, and CT Yard conductors, on the other hand.3 N & W is neutral in the dispute and specifically disclaims any valid business reason to prefer plaintiffs’ plan of merger over the merger effected by- the district court and supported by the unions, or vice versa. We think that for the two affected classes, plaintiffs’ merger of the seniority rosters should be decreed, subject of course to actual qualification as conductors by those Barney Yard brakemen hired between March 18, 1956 and September 18, 1963, who have never had the opportunity to qualify for conductor.
To understand our conclusion, additional facts should first be stated. In both yards, when N & W determines the need for additional conductors, brakemen have the opportunity to qualify in the order of their brakemen seniority. Since the need for conductors in the particular yard fluctuates, the length of time brakemen must be employed as brakemen before having the opportunity to bid for promotion also varies.
The record reflects that CT Yard brakemen gained the chance to promote to conductors far more rapidly than Barney Yard brakemen. By April, 1971, every CT Yard brakeman hired on or before September 18, 1963, had been offered the opportunity to be promoted to conductor. Most CT Yard brakemen hired before 1964 were promoted to conductor after 6-7 years as brakemen— three within three years. No Barney Yard brakeman hired after March 18, 1956, had, by April 1971, any opportunity to become a conductor. Most Barney Yard brakemen who had received a chance to be promoted waited a period of 8-15 years after first employment as a brakeman to receive an opportunity to bid for promotion.
Because Barney Yard brakemen have enjoyed fewer and slower opportunities for promotion to conductor, all Barney Yard brakemen hired between March 18, 1956, and September 18, 1963, who have never had the opportunity to qualify as conductors, as have CT Yard brakemen hired in this period, and those Barney Yard brakemen hired before March 18,1956, who have been promoted to conductor, carry a later seniority date than similarly situated CT Yard conductors.
Given the discrimination in employment between the two yards as found by the district court and affirmed in the first appeal, reinforced by the additional facts that we have recited, we think that the district court’s merger of the seniority rosters with respect to conductors of the affected classes (both present and future) will preserve and perpetuate past discrimination. Present Barney Yard conductors of the affected class will forever suffer a loss of seniority compared to their CT Yard counterparts. Barney Yard brakemen of the affected class who may hereafter qualify as a conductor can never overcome the disadvantage in seniority that that discrimination inflicted. The case strongly resembles United States v. Chesapeake & Ohio Railway Co., 471 F.2d 582, 588-89 (4 Cir.), cert. denied, 411 U.S. 939, 93 S.Ct. 1893, 36 L.Ed.2d 401 (1973), where we held that “topping and bottoming” was not an adequate remedy to eliminate the racial discrimination that initially barred brakemen from becoming conductors. In short, the proposed means of merging the conductors’ seniority lists fails to effectuate our prior mandate in this case to protect “Barney Yard brakemen from prejudice in connection with promotion to [conductors].” 473 F.2d at 1349.
The plaintiffs propose their own merger plan and the union advocates that adopted by the district court; N & W says either is feasible. Others may be devised, but we do not stop to construct them. They were not presented to the district court and they are not urged on appeal. Because of the com[344]*344plexities of the issue, we prefer not to go beyond the alternatives which N & W says are workable.
We think that plaintiffs’ proposed merger of seniority rosters would be in accord with our prior mandate. It will redress discriminatory loss of seniority on the part of Barney Yard conductors in one of the affected classes, and it will make possible nondiscriminatory promotion of Barney Yard brakemen in the other affected class—all without giving members of either class any broader or greater rights than those possessed by CT Yard conductors. On remand, the district court will amend its decree in this respect accordingly.
III.
Finally, we turn to the assertion that minimum wage guarantees made to certain N & W employees in 1964 when Nickel Plate Railroad was merged with N & W should be extended to certain of the plaintiffs. As part of the merger agreement N & W and the unions agreed that each yardman employed by N & W as of October 1964 would be guaranteed the same level of average monthly earnings as he enjoyed in the one-year period immediately prior to the merger. The minimum wage guarantee agreement is not applicable to yardmen hired after October 16, 1964. The Interstate Commerce Commission adopted this agreement in approving the merger. Under the agreement each N & W yardman submits a claim for additional compensation showing his “test” wage and his actual earnings for the month pertinent to the claim. If his actual earnings are less than his “test” wage, he must assert his availability for more work had it been available, and overall the computation must show the amount due him, i. e., the difference between guaranteed wage and actual earnings. If the employee failed to accept work that he would otherwise have received, his claim to the minimum wage is forfeited to the extent that he declined to work.
With respect to Barney Yard brakemen whose opportunities for work and for promotion at the Barney Yard were less than those of their counterparts at the CT Yard, we have previously shown that they have suffered discrimination which is reflected in their total compensation. In any month in which there was insufficient work for all yardmen at both yards, Barney Yard men employed prior to October 16, 1964, suffered further discrimination in that their guaranteed monthly wage was less than the guaranteed monthly wage of their counterparts at the CT Yard. It follows, we think, that to redress fully the discriminations which have been practiced against it, this group should be treated as if the minimum wage guarantee had extended to it. This is only a ramification of our general holding that the back pay awards due Barney Yard men should be measured according to what they would have earned had they been employees at the CT Yard prior to October 16, 1964. See Bowe v. Colgate, Palmolive Co., 489 F.2d 896, 903-04 (7 Cir. 1973); Peters v. Missouri-Pacific Railroad Co., 483 F.2d 490, 498-99 (5 Cir.), cert. denied, 414 U.S. 1002, 94 S.Ct. 356, 38 L.Ed.2d 238 (1973); Rosen v. Public Service Electric & Gas Co., 477 F.2d 90, 95-96 (3 Cir. 1973).
Albemarle Paper Co. v. Moody, 422 U.S. 405, 95 S.Ct. 2362, 45 L.Ed.2d 280 (1975); Griggs v. Duke Power Co., 401 U.S. 424, 430, 91 S.Ct. 849, 28 L.Ed.2d 158 (1971), and our decisions in Chesapeake and Ohio Railroad Co. and Robinson establish that Title VII requires elimination of all continuing effects of past discrimination. Subject only to our later discussion that Barney Yard employees’ prosecution of this aspect of their claim to back pay may have prejudiced the parties liable therefor to the extent that recovery should be denied, we think that application of the Nickel Plate Merger Agreement to increase monthly guarantees to Barney Yard employees equivalent to guarantees granted CT Yard employees of comparable seniority falls within the scope of settled law.
The district court declined to consider the claimed extension of the Nickel Plate Merger Agreement on the ground that the claim was untimely, saying “[a]t no time prior in the four-year record of this case before this [345]*345Court has there been any mention of guarantees under the Nickel Plate Merger Plan, that is, until February 8, 1974, or final argument of the matter on remand. We deem it inappropriate to move to new material at this late date.”
Before us, N & W argues that Barney Yard employees must have known before the first remand of the guarantees made to CT Yard men, but Barney Yard employees did not assert the claim until N & W invoked the Nickel Plate Minimum Compensation Agreement to support its argument that a provision should be included in the dovetailed seniority lists prohibiting N & W from requiring a CT Yard employee to work at the Barney Yard even if there were no work available at the CT Yard. N & W thus urges the correctness of the district court’s treatment of the issue.
In Albemarle Paper Co., the district court denied a claim for back pay, inter alia, because it was not asserted until five years after the complaint was filed and the employer was thereby “prejudiced.” The Court held that “a party may not be ‘entitled’ to relief if its conduct of the cause has improperly and substantially prejudiced the other party. ... To deny backpay because a particular cause has been prosecuted in an eccentric fashion, prejudicial to the other party, does not offend the broad purposes of Title VII.” 422 U.S. at 424, 95 S.Ct. at 2375. In that case the issue was remanded to the district court for a specific determination of “[wjhether the petitioners [employers] were in fact prejudiced, and whether the respondents’ [employees’] trial conduct was excusable . . . . 422 U.S. at 424, 95 S.Ct. at 2375. Thus, Albemarle recognizes that a claim for back pay may be forfeited if it is inexcusably pressed under such circumstances as prejudice the employer.
Aside from its statement that in the view of the district court plaintiffs were late in asserting any claims arising from the Nickel Plate Minimum Compensation Agreement, the factual bases on which a late back pay claim may properly be denied were not considered. Specifically, the district court made no finding of whether lateness, if that be found, was excusable and, if not, whether N & W was prejudiced. As in Albemarle Paper Co., these are questions for the district court in the first instance and should be considered on remand. We will remit them to the district court, cautioning only that Albemarle Paper Co. teaches “[i]t is necessary . . . that if a district court does decline to award back-pay, it carefully articulate its reasons.” 422 U.S. 405 at 421, 95 S.Ct. 2362 at 2373, n.14.
Accordingly, we hold that, unless it be found that the circumstances of assertion of the claim have been prejudicial to N & W such as to warrant barring its allowance, in the computation of back pay for Barney Yard employees the Nickel Plate Merger Agreement be given effect and that employees be entitled to back pay to the extent that they can demonstrate that they failed to earn the minimum wage guarantees afforded their counterparts at the CT Yard.
VACATED AND REMANDED.