Opinion ID: 438801
Heading Depth: 2
Heading Rank: 2

Heading: Analysis of the Liability Issues

Text: 62 For the sake of clarity and congruence with the form of argument presented to us, we will separate our analysis along the lines suggested by the parties' arguments. First we will examine the sufficiency of plaintiffs' offer of proof in light of DEA's attack on the methodology and results of plaintiffs' statistical analyses. Then we will examine the strength of DEA's evidence, and consider DEA's allegations of error. Both lines of inquiry must, however, lead us toward resolution of the ultimate issue: In weighing all the evidence, did the trial court correctly conclude that plaintiffs carried their burden of persuasion as to the existence of illegal discrimination at DEA. 20 Also, to the extent DEA's rebuttal raises issues as to the business necessity of its employment practices, we will resolve these issues in accordance with Griggs and its progeny. 63 1. The sufficiency of plaintiffs' initial case. A general principle of disparate treatment adjudication requires the plaintiff to carry the initial burden of offering evidence adequate to create an inference that an employment decision was based on a discriminatory criterion illegal under the Act. Teamsters, supra, 431 U.S. at 358, 97 S.Ct. at 1866. Because [t]he facts necessarily will vary in Title VII cases, McDonnell Douglas Corp., supra, 411 U.S. at 802 n. 13, 93 S.Ct. at 1824 n. 13, a specific test for the sufficiency of a plaintiff's initial proof is not possible. Teamsters, supra, 431 U.S. at 358, 97 S.Ct. at 1866. Rather, a plaintiff's initial proof must be measured against the more generalized functional standard that the Supreme Court has elaborated in Teamsters, supra, 431 U.S. at 358, 97 S.Ct. at 1866; Furnco Construction Corp. v. Waters, 438 U.S. 567, 577, 98 S.Ct. 2943, 2949, 57 L.Ed.2d 957 (1978), and Burdine, supra, 450 U.S. at 253-254, 101 S.Ct. at 1093-1094. These cases hold that a sufficient prima facie case is made out when the plaintiff shows a disparity in the relative position or treatment of the minority group and has eliminated the most common nondiscriminatory reasons for the observed disparity. Burdine, supra, 450 U.S. at 253-254, 101 S.Ct. at 1093-1094; accord Furnco, supra, 438 U.S. at 579-580, 98 S.Ct. at 2951 (A prima facie case is simply proof of actions taken by the employer from which we infer discriminatory animus because experience has proved that in the absence of any other explanation it is more likely than not that those actions were bottomed on impermissible considerations). 64 The present case typifies class actions alleging a pattern or practice of discrimination in that the plaintiffs' argument is largely bottomed on statistical evidence comparing the percentage and distribution of minorities in the employer's workforce to the percentage of minorities in the labor pool from which the employer is able to draw. To be legally sufficient these statistics must show a disparity of treatment, eliminate the most common nondiscriminatory explanations of the disparity, and thus permit the inference that, absent other explanation, the disparity more likely than not resulted from illegal discrimination. Teamsters, supra, 431 U.S. at 368, 97 S.Ct. at 1871. 65 A pattern or practice case challenges a host of employment decisions over time; in effect, it challenges an employment system. The most common nondiscriminatory explanation for a systemic disparity in treatment is a lack of qualifications among the minority group members. A plaintiff's statistical evidence must therefore focus on eliminating this nondiscriminatory explanation by showing disparities in treatment between individuals with comparable qualifications for the positions at issue. Hazelwood School District, supra, 433 U.S. at 308 n. 13, 97 S.Ct. at 2742 n. 13; DeMedina v. Reinhardt, 686 F.2d 997, 1007 (D.C.Cir.1982) (quoting D. Baldus & J. Cole, supra, at 120). 66 Once the plaintiffs' analysis has focused on the proper groups for comparison, it must yield results that meet generally accepted standards of statistical significance. In other words, both the methodology and the explanatory power of the statistical analysis must be sufficient to permit an inference of discrimination. 67 a. Methodology: minimum objective qualifications. To ensure that a plaintiff's methodology has eliminated the common nondiscriminatory explanation of a lack of qualifications, this circuit has developed a requirement that statistical evidence of disparities account for the minimum objective qualifications for the positions at issue. DeMedina, supra, 686 F.2d at 1003; Valentino, supra, 674 F.2d at 71; Davis v. Califano, supra, 613 F.2d at 964. This requirement greatly aids evaluation of regression analyses such as those used here. Regressions seek to prove race discrimination by testing possible alternative explanations for an observed disparity between blacks and whites, and typically these alternative explanations will be particular employee traits such as prior experience or education. The minimum objective qualification approach should not, however, be read as a hard and fast rule; tests for the sufficiency of a Title VII prima facie case must not be applied in a rigid, mechanistic, or ritualistic way. Furnco, supra, 438 U.S. at 577, 98 S.Ct. at 2949. The minimum objective qualification approach is not a quick litmus test, but an analytic method to ensure that a plaintiff's statistics measure disparities among comparably qualified workers, rather than disparities in qualifications. The ultimate test of sufficiency must remain that of Burdine, Teamsters, and Furnco: did the plaintiffs offer evidence adequate to create an inference that    employment decision[s]    [were] based on a discriminatory criterion illegal under the Act. Teamsters, supra, 431 U.S. at 358, 97 S.Ct. at 1866. Accord Burdine, supra, 450 U.S. at 253-254, 101 S.Ct. at 1093-1094; Furnco, supra, 438 U.S. at 577, 98 S.Ct. at 2949; Valentino, supra, 674 F.2d at 74 (statement of Wald, J. on denial of rehearing) (In each case, the critical question is whether there is a reasonable basis for inferring disparate treatment.). 68 In the present case DEA has challenged plaintiffs' salary regression analyses on the ground that they fail to account for a minimum objective qualification: specialized prior experience in criminal investigations. The burden of DEA's argument is that the failure to include this factor skewed all of plaintiffs' studies because the lower salaries and less rapid promotions of black agents can in large measure be traced to the fact that black agents lack prior criminal investigative experience and therefore enter DEA at a lower grade level. This court must determine whether the failure of plaintiffs' analyses to account specifically for this factor precludes an inference of discrimination under the functional test of Burdine, Teamsters, and Furnco. Although we review the trial court's findings of fact on the clearly erroneous standard, Albemarle Paper Co., supra, 422 U.S. at 424, 95 S.Ct. at 2374, the issue whether a Title VII plaintiff has included necessary variables in statistical proof trigger[s] a more careful examination   . Trout v. Lehman, 702 F.2d 1094, 1101 (D.C.Cir.1983), vacated on other grounds, --- U.S. ---, 104 S.Ct. 1404, 79 L.Ed.2d 732 (1984). We must therefore delve somewhat deeply into DEA's initial grade assignment practices. 69 Special agents enter DEA at either the GS-7 or the GS-9 level. The requirements for the two entry levels are set forth in the Civil Service Commission Handbook, x-118, and have been summarized in a stipulation of the parties, Joint Exhibit I, JA 39. The requirements for GS-7 are three years of general experience and one year of specialized experience. JA 39. The requirements for GS-9 are three years of general experience and two years of specialized experience. Id. General experience is defined as: 70 [P]rogressively responsible experience which has required (1) ability to work or deal effectively with individuals or groups of persons; (2) skill in collecting and assembling pertinent facts; (3) ability to prepare clear and concise reports; and (4) ability and willingness to accept responsibility. Id. Specialized experience is defined as: 71 [P]rogressively responsible investigative experience which demonstrates (1) initiative, ingenuity, resourcefulness, and judgment required to collect, assemble and develop facts and other pertinent data; (2) ability to think logically and objectively, to analyze and evaluate facts, evidence, and related information, and arrive at sound conclusions; (3) skill in written and oral reports and presentation of investigative findings in a clear and concise manner; and (4) tact, discretion, and capacity for obtaining the cooperation and confidence of others. 72 Id. at 40. In addition, special agents at both GS-7 and GS-9 are criminal investigators, JA 41, and one year of their prior specialized experience must be in criminal investigative work or other comparable work. JA 40. 73 Extrapolating, we see, first, that every special agent hired, whether at GS-7 or GS-9, must have at least one year of prior specialized experience in criminal investigative work, and, second, that the only difference between those hired at GS-7 and those hired at GS-9 is one additional year of specialized experience as defined above. According to the stipulation, this additional year need not be in criminal investigations. 74 These facts severely undermine DEA's argument. The claim that plaintiffs' statistics have wholly failed to account for prior experience in criminal investigations is inaccurate. Plaintiffs studied only those whom DEA had already hired. Every one of them must have met the basic Civil Service requirement of one year of prior criminal investigative experience to have been hired even at the GS-7 level. Thus DEA's claim that plaintiffs' studies took no account of basic experiential requirements, brief for appellants at 60, is incorrect according to the facts to which DEA stipulated. Plaintiffs' studies did not specifically account for criminal investigative experience over and above this one year that all special agents possess. But--again according to the stipulated facts--criminal investigative experience above the one year minimum is not a requirement for entry at GS-9 instead of GS-7. Rather, the additional requirement for entry at GS-9 is a second year of specialized experience as defined in the Civil Service Commission Handbook. Plaintiffs' failure explicitly to account for additional years of prior criminal investigative experience therefore cannot be viewed as an omission of a minimum objective qualification. 75 The only possible omission of a minimum objective qualification in this case would be plaintiffs' failure to account specifically for the requirement of an additional year of specialized experience, as defined in the Civil Service Commission Handbook. For three reasons, we hold that the District Court's approval of plaintiffs' decision to exclude this variable from their analyses was not erroneous. 76 First, the operative Civil Service definition of specialized experience is highly subjective. It measures such intangibles as ingenuity, resourcefulness, ability to arrive at sound conclusions, tact, and discretion. JA 40. The law is clear that a plaintiff's proof must account for objective qualifications; exclusion of subjective requirements, such as those encompassed in the definition of specialized experience, is entirely proper. See Davis v. Califano, supra, 613 F.2d at 964. The reason for exclusion is equally clear. Such subjective criteria may well serve as a veil of seeming legitimacy behind which illegal discrimination is operating. If so, measurement of the relation of such a factor to an observed disparity would simply amount to a measure of the amount of discrimination operating through application of the factor. See Vuyanich I, supra, 505 F.Supp. at 277; James v. Stockham Valve & Fitting Co., 559 F.2d 310, 331-333 (5th Cir.1977); Finklestein, The Judicial Reception of Multiple Regression Studies in Race and Sex Discrimination Cases, 80 COLUM.L.REV. 737, 738-742 (1980). Cf. Valentino, supra, 674 F.2d at 73 n. 30 (failure to include (GS) grade level as a variable in regression analysis is proper; absent clear, affirmative evidence that promotions were made in accordance with neutral, objective standards consistently applied, there is no assurance that level or rank is an appropriate explanatory variable untainted by discrimination). 77 Second, plaintiffs were not realistically able to account for the application of so amorphous a criterion as the Civil Service definition of specialized experience. This circuit has recognized that [t]he appropriate degree of refinement of the plaintiffs' statistical analysis    may depend on the quality and control of the available data. Trout v. Lehman, supra, 702 F.2d at 1101. Plaintiffs here relied on the objective evidence available to them--the Justice Department's JUNIPER tapes--to construct their analytical models. Based on this and other evidence reasonably available to them, they could not possibly have quantified the applicable Civil Service requirement of specialized experience in a manner that would have made the requirement amenable to statistical analysis. Perhaps DEA has distilled objective proxies for specialized experience--such as prior police experience--that might have been quantifiable, but the record is devoid of any evidence that DEA has in fact done so. Both the policies underlying Title VII and general principles of evidence suggest that the burden of production of such evidence must rest with the defendant. See Trout v. Hidalgo, 517 F.Supp. 873, 883 & n. 33 (D.D.C.1981) ([o]ne clear purpose of discrimination law is to force employers to bring their employment processes into the open), aff'd, 702 F.2d 1094 (D.C.Cir.1983), vacated on other grounds, --- U.S. ----, 104 S.Ct. 1404, 79 L.Ed.2d 732 (1984); EEOC v. Radiator Specialty Co., 610 F.2d 178, 185 n. 8 (4th Cir.1979) (Title VII case following principle of allocation of proof to the party with the most ready access to the relevant information); DeMedina, supra, 686 F.2d at 1008, 1009 & n. 7. 78 Third, even if we accept arguendo that a second year of specialized experience--or, for that matter, of criminal investigative experience--is a minimum objective qualification, DEA's objections would still fall short in a crucial respect. A strong argument exists that plaintiffs' regressions have implicitly accounted for this variable. Apart from the unsubstantiated declamations of DEA's appellate attorneys, nothing in the record so much as hints that black special agents are less likely than white special agents to possess this qualification. The labor pool that plaintiffs' experts studied comprised only those whom DEA had already hired. All of these individuals had at least one year of prior criminal investigative experience. There is simply no reason to assume that the blacks in such a group of trained, experienced law enforcement officials are less likely than the whites in the same group to have had a second year of specialized experience or prior criminal investigative experience. Nor has DEA articulated    [a] basis for the assumption that such skills are in fact unevenly distributed   . DeMedina, supra, 686 F.2d at 1008. In an analogous situation the court in DeMedina established a rebuttable presumption of an equal distribution of the relevant    skills. Id. (emphasis in original). Such a presumption is equally appropriate here. 79 This high degree of homogeneity of qualifications among those in the labor pool distinguishes the present case from Valentino, supra, where the court did not employ a presumption of equal qualifications. In Valentino the court found that [i]n the setting [of the case] it would be irrational to assume 'equal qualifications' to fill engineering or secretarial vacancies among persons educated the same number of years and employed by the government for the same length of time. 674 F.2d at 71 (footnotes omitted). In other words, the heterogeneity of the labor pool that plaintiff defined precluded any presumption of equal qualifications. In the present setting, by contrast, it would be irrational to assume unequal qualifications. 80 Since DEA has presented no admissible evidence that black agents are more likely than white agents to lack a second year of requisite experience, plaintiffs' failure to account for this variable does not dilute the force of their statistical analysis; in the language of the statistician, absent any reason to conclude that the omitted factor correlates with race, the omission of the variable will not affect the validity of the race coefficient in plaintiffs' regression analysis. See D. Baldus & J. Cole, supra, at 273; Vuyanich I, supra, 505 F.Supp. at 274. 81 Though any one of the above reasons would have justified plaintiffs' decision to exclude specialized experience as a variable, we note the multiplicity of proper objections to use of this criterion in order to highlight the weakness of this aspect of DEA's challenge. In sum, plaintiffs' statistical proof cannot be faulted for any failure to focus on a population that closely approximates the characteristics of those eligible for the positions at issue. DeMedina, supra, 686 F.2d at 1007. By studying only those whom DEA had already hired, plaintiffs' experts ensured in this case that the group analyzed would possess a relatively similar composite of skills and experience. Thus, on the methodological level, the District Court correctly concluded that plaintiffs' evidence meets the functional test of Teamsters, Furnco, and Burdine. 82 b. Explanatory power. DEA also challenges the explanatory power of plaintiffs' statistical evidence. As a threshold matter DEA argues that because the trial court did not credit any of plaintiffs' specific anecdotal accounts of discrimination, see Part I-C & n. 10 supra, plaintiffs could not make out a prima facie case unless their statistics showed gross disparities of treatment. See Hazelwood School District, supra, 433 U.S. at 307-308, 97 S.Ct. at 2742. We must therefore decide at the outset whether plaintiffs' lack of anecdotal evidence triggers a requirement that plaintiffs show gross disparities of treatment. Beyond this threshold issue DEA argues that plaintiffs' statistics do not show sufficient actionable post-1972 discrimination at sufficient levels of statistical significance to support an inference of discrimination. Thus we must also decide whether the District Court properly found that plaintiffs had made a sufficient showing of actionable discrimination, both in terms of the magnitude of actionable disparities and in terms of the level of statistical significance. 83 i. The effect of a lack of anecdotal evidence. Anecdotal testimony recounting personal experiences of discrimination plays an important role in Title VII litigation. Such testimony may '[bring] the cold numbers convincingly to life.'  Valentino, supra, 674 F.2d at 68 (quoting Teamsters, supra, 431 U.S. at 338-339, 97 S.Ct. at 1856). The presence of anecdotal testimony bolsters a plaintiff's case, and may become crucial when the statistical evidence does not adequately account for 'the diverse and specialized qualifications necessary for [the positions in question].'  Valentino, supra, 674 F.2d at 69 (quoting Wilkins v. University of Houston, 654 F.2d 388, 410 (5th Cir.1981)). 84 DEA urges that the converse is equally true; when anecdotal evidence is lacking, statistical evidence must show, as a matter of law, not merely disparities in treatment, but gross disparities. This argument derives from one sentence in Hazelwood School District, supra: Where gross statistical disparities can be shown, they alone may in a proper case constitute prima facie proof of a pattern or practice of discrimination. 433 U.S. at 307-308, 97 S.Ct. at 2742. Drawing from this sentence a fixed rule that only gross disparities suffice absent anecdotal testimony, DEA reads the words for all they are worth, and more. 85 Neither Hazelwood nor any other Supreme Court precedent supports a rule that statistical proof of the kind presented in this case is insufficient absent anecdotal evidence. To make a prima facie case plaintiffs must meet the functional standard of Teamsters, Burdine, and Furnco; they must present evidence sufficient to support an inference of discrimination. All evidence that a plaintiff presents can contribute to this inference, and should therefore be considered as cumulative. EEOC v. American National Bank, 652 F.2d 1176, 1188 (4th Cir.1981) (reliance on cumulation of evidence including statistics, patterns, practices, general policies or specific instances of discrimination), cert. denied, 459 U.S. 923, 103 S.Ct. 235, 74 L.Ed.2d 186 (1982). Though anecdotal evidence might bolster a plaintiff's case or reduce the need for strong statistical proof, see Valentino, supra, 674 F.2d at 69, neither the presence nor the absence of specific anecdotal accounts alters the standard that a plaintiff's initial case must meet. 86 Read in context the language in Hazelwood on which DEA places so much weight will not bear the meaning DEA seeks to impose on it. In the immediately preceding passage the Court, quoting from Teamsters, stated: Evidence of longlasting and gross disparity between the composition of a workforce and that of the general population may thus be significant   . 433 U.S. at 307, 97 S.Ct. at 2741 (quoting Teamsters, supra, 431 U.S. at 340 n. 20, 97 S.Ct. at 1856 n. 20) (emphasis added). The language to which DEA points refers back to this preceding sentence. Thus, if the Court intended any specific rule by the gross disparity language, the Court meant that rule to apply when a plaintiff relies on general population/workforce comparisons and lacks anecdotal evidence. Such a requirement might be appropriate because a population/workforce comparison will usually yield only rough evidence of discrimination; the method is not finely tuned to the population of those eligible for and interested in the positions at issue. Absent anecdotal evidence, an inference of discrimination is less secure when such statistics show only slight disparities. When, however, statistical evidence is more finely tuned to the relevant labor pool, gross disparities need not be shown to permit an inference of discrimination. See B. SCHLET & P. GROSSMAN, EMPLOYMENT DISCRIMINATION LAW 1371 (1983). 87 Statistics, of course, are not irrefutable, Teamsters, supra, 431 U.S. at 340, 97 S.Ct. at 1856, but when a plaintiff's statistical methodology focuses on the appropriate labor pool and generates evidence of discrimination at a statistically significant level, no sound policy reason exists for subjecting the plaintiff to the additional requirement of either providing anecdotal evidence or showing gross disparities. Such a rule would reflect little more than a superstitious hostility to statistical proof, a preference for the intuitionistic and individualistic over the scientific and systemic. It is not difficult to understand that discrimination might exist even when affected individuals can point to no specific instances of an employer's discriminatory conduct. The days of Bull Connor are largely past; discrimination now works more subtly. Yet its effects are no less pernicious.  'In many cases the only available avenue of proof is the use of racial statistics to uncover clandestine and covert discrimination   .'  Teamsters, supra, 431 U.S. at 340 n. 20, 97 S.Ct. at 1856 n. 20 (quoting United States v. Ironworkers Local 86, 443 F.2d 544, 551 (9th Cir.1971)). Statistical proof, crucial to advancing the purposes of Title VII, must not be encumbered with requirements such as those DEA urges here. 88 In the present case plaintiffs rely on statistical evidence that has been demonstrated to be fine-tuned to the relevant labor pool. See Part II-B-1-a supra. This case is, in other words, a far cry from Hazelwood. If plaintiffs' statistical proof standing alone permits an inference that DEA's employment decisions were more likely than not based on race, then this proof suffices irrespective of the presence of supporting anecdotal evidence. Moreover, were we to require anecdotal evidence plaintiffs would still meet their prima facie burden. Although DEA adequately rebutted most testimony regarding specific instances of discrimination, 508 F.Supp. at 690, 713, the trial court credited much of plaintiffs' nonstatistical evidence, including the testimony of several agents about disparate treatment in disciplinary procedures and supervisory evaluations, and about black agents' general perceptions that DEA was a discriminatory environment. Id. at 708-711. 89 ii. The sufficiency of plaintiffs' showing of disparities. Although plaintiffs need not show enhanced or gross disparities, they must present evidence that permits an inference of discrimination under the test of Burdine, Teamsters, and Furnco. DEA raises two issues with respect to the sufficiency of plaintiffs' showing under this test. The first issue involves the magnitude of actionable discrimination shown in plaintiffs' statistics; DEA argues that the District Court improperly relied on nonactionable pre-1972 discrimination reflected in the statistics in finding a prima facie case of discrimination. The second issue involves the statistical significance of the disparities in plaintiffs' regressions. 90 The magnitude of actionable disparity. DEA has made a very cursory argument that appellees' statistical showing is flawed because the statistics in part reflect pre-1972 discrimination. The brevity of DEA's analysis offers little clue as to the import of this alleged flaw. We do not understand DEA to be contending that the District Court based its finding of discrimination on the erroneous legal premise that pre-1972 discrimination was independently actionable, for the court explicitly indicated that Title VII is applicable to DEA only for post-1972 discrimination. Findings p 7d, 508 F.Supp. at 696. Nor do we understand DEA to be contending that statistical evidence reflecting both pre-1972 discrimination and post-1972 discrimination cannot, as a matter of law, suffice to support an inference of post-1972 discrimination. See Valentino, supra, 674 F.2d at 71 n. 26 ([F]ailure to factor out time-barred discrimination [does not] discredit the analyses. Statistics tuned to the proper time period are more probative than statistics not so tuned, but categorical rejection of the latter is not warranted[.]); Movement for Opportunity and Equality v. General Motors Corp., 622 F.2d 1235, 1258 (7th Cir.1980). Finally, DEA has not even suggested that the District Court did not base its liability determination independently on evidence that did not reflect pre-1972 discrimination. 91 Despite the shortcomings of DEA's analysis, we have considered with care the possibility that erroneous consideration of pre-1972 discrimination may have infected the lower court's liability determination. This question commands our attention in light of the Supreme Court's recent decision in another Title VII case, Lehman v. Trout, --- U.S. ----, 104 S.Ct. 1404, 79 L.Ed.2d 732 (1984). In Trout the Court vacated this circuit's affirmance of a District Court finding of discrimination based largely on evidence reflecting both pre- and post-1972 discrimination. To understand the relevance of the Supreme Court's holding to the present case we must trace the course of the court decisions in Trout. 92 Though the plaintiffs' statistics in Trout reflected both pre- and post-1972 discrimination, the District Court found the statistics sufficient to support an inference of post-1972 disparate treatment. In dismissing the defendants' objection to the use of the pre-1972 data the court indicated, inter alia, that [i]t is likely that such discrimination before 1972, even if coupled with neutral employment practices since then, produced actionable continuing discriminatory effects after 1972   . Trout v. Hidalgo, supra, 517 F.Supp. at 880. On appeal this court held that the District Court's continuing effects theory was flatly inconsistent with the Supreme Court's earlier pronouncements. Trout v. Lehman, supra, 702 F.2d at 1104. However, because the record indicated to us that the District Court had found, in the alternative, that post-1972 statistics were sufficient to support an inference of disparate treatment, see Trout v. Hidalgo, supra, 517 F.Supp. at 879 n. 14, we affirmed the court's liability determination. 93 Although the Supreme Court found no fault with our understanding of Title VII principles in Trout, the Court vacated and remanded to this court with instructions to remand to the District Court for findings of fact, based on new evidence if necessary, on the question what evidentiary value respondents' and petitioners' statistical evidence has in light of the Court of Appeals' conclusions of law concerning employment decisions that are not actionable in this case. See Pullman-Standard v. Swint, 456 U.S. 273, 292, 102 S.Ct. 1781, 1792, 72 L.Ed. 66 (1982). Lehman v. Trout, supra, --- U.S. at ----, 104 S.Ct. at 1404. Though the Court's opinion was exceedingly brief and its citation to Pullman-Standard was unexplained, this citation implies that the Court was acting out of an abundance of caution to protect the sanctity of the trial court's factfinding function. See Pullman-Standard v. Swint, supra, 456 U.S. at 292, 102 S.Ct. at 1792. We therefore infer that, in Trout, the Court was unsure whether the trial court would have found discrimination absent its erroneous understanding as to the legal significance of continuing effects. Hence the remand. 94 At least in the context of this case, the message to be gleaned from Trout is that we must proceed with caution if the trial court has made an error of law in finding discrimination, lest we invade the factfinding prerogative of the District Court. If the District Court has found a prima facie case of discrimination because of an erroneous view of the law, Pullman-Standard, supra, 456 U.S. at 292, 102 S.Ct. at 1792 (emphasis added), this court may not take upon itself the task of deciding in the first instance whether the facts nonetheless support an inference of discrimination under a correct understanding of the law. 95 In this case we have no trouble concluding that the teachings of Pullman-Standard and Trout do not warrant reversal of the District Court on the ground that the court used some statistics that might reflect pre-1972 discrimination. DEA has not argued on appeal that the use of data reflecting pre-1972 discrimination affected any aspect of the District Court's liability determination other than the findings of salary disparities. 21 Hence, even if DEA's argument were well-placed, most of the District Court's liability determination would remain intact. Specifically, DEA has not suggested that this argument has any application to the District Court's independent findings that plaintiffs established a prima facie case of discrimination in grade-at-entry, work assignments, supervisory evaluations, discipline, and promotions. See 508 F.Supp. at 712-715. And even with respect to the plaintiffs' prima facie proof of salary disparities further factfinding by the District Court is unnecessary. It is far from clear whether the court erroneously reasoned that any disparities resulting from the continuing effects of pre-1972 discrimination were actionable. 22 However, assuming arguendo that such a legal error was made, it is clear that the trial court did not make its finding of a prima facie case of salary discrimination because of  any such erroneous view. Two considerations compel this conclusion. 96 First, as we have explained, the court properly could consider evidence that may have reflected pre-1972 discrimination in determining that a prima facie case was established. In considering plaintiffs' first regression, which included data on employees hired before 1972, the court acknowledged that it was theoretically possible that pre-1972 discrimination might affect the regression. Findings p 7h, 508 F.Supp. at 697. The court, however, expressly found that this effect was unproven 23 and that it might cause the regression to underestimate the extent of post-1972 discrimination. 24 The trial court concluded that DEA's failure to test this hypothesis empirically left DEA's criticism speculative and incapable of rebutting Plaintiffs' statistical showing. 25 Moreover, based on the second regression (analyzing agents hired after 1972) the court found that post 1972 discrimination largely contributed to the statistical results in the first regression. Findings p 7i, 508 F.Supp. at 697. 97 Given these factual findings the lower court certainly could, and did in fact, permissibly conclude that the first regression established a prima facie case of post-1972 discrimination, and these findings plainly indicate that the District Court did not consider a continuing effects theory to be essential to its finding that a prima facie case of post-1972 discrimination was established. 98 Second, the District Court's finding that plaintiffs established a prima facie case of discrimination in salaries was independently based on statistics pertaining only to employees hired after 1972. The court reviewed these statistics and found that the salary disparities were statistically significant at or below the .05 level for every year since 1975. Findings p 7d, 508 F.Supp. at 696. It also found that these statistics tend to downplay the effects of discrimination at DEA because almost half the agents in the 1975 analyses were hired in 1974, and the most serious promotional problems are encountered in the middle and upper grades. Findings p 7e, 508 F.Supp. at 696. The court concluded that these statistics evidenced gross salary disparities, and that because of these disparities plaintiffs had established a prima facie case of salary discrimination. 26 99 In light of the foregoing, we conclude that consideration of some data that might hypothetically reflect continuing effects of pre-1972 discrimination does not dictate reversal of the District Court's liability determination. The District Court's opinion clearly indicates that the court based this determination independently on evidence that did not reflect such discrimination. DEA has not argued otherwise. In these circumstances, due regard for the trial court's role as finder of fact requires us to respect the independent bases on which the District Court grounded its liability determination. Accordingly, we conclude that the court's findings are not infirm because of an erroneous view of the law. Pullman-Standard, supra, 456 U.S. at 292, 102 S.Ct. at 1792. 100 The statistical significance of the disparities shown. DEA also argues that plaintiffs' salary regressions did not achieve a level of statistical significance sufficient to permit an inference of discrimination. 27 The notion of statistical significance addresses directly the question whether an inference of discrimination is warranted. Statistical significance is a measure of the probability that the outcome of a statistical analysis would have occurred by chance: The lower the probability that the observed outcome could have occurred by chance, the stronger the inference of discrimination that can be drawn from the data. For example, a finding that a study is significant at the .10 level indicates that the odds are one in ten that the result could have occurred by chance, and a finding of significance at the .05 level indicates that the odds are one in 20 that the result could have occurred by chance. Although the law has not set any precise level at which statistical significance can be said to be sufficient to permit an inference of discrimination, social scientists usually accept a study that achieves statistical significance at the .05 level. D. Baldus & J. Cole, supra, at 297; cf. F. MOSTELLER, R. ROURKE & G. THOMAS, PROBABILITY WITH STATISTICAL APPLICATIONS 310 (2d ed. 1970). In other words, a study is found significant--and the hypothesis of chance is rejected--when there exists at most a one in 20 possibility that the observed result could have occurred by chance. Several courts have adopted the .05 level as sufficient to support an inference of discrimination in Title VII cases. Vuyanich I, supra, 505 F.Supp. at 271; Cooper v. University of Texas, 482 F.Supp. 187, 194 (N.D.Tex.1979). The Justice Department itself has adopted the .05 standard as sufficient in this area. See Uniform Guidelines on Employee Selection Sec. 14(B)(5), 43 Fed.Reg. 38290, 38301 (1978); 28 C.F.R. Sec. 50.14 (1983). 28 101 Without deciding whether a plaintiff's initial case might suffice even without meeting the .05 level of significance, 29 we find that the plaintiffs in this case have presented analyses that meet the generally accepted .05 level of statistical significance. All findings of plaintiffs' salary regressions meet or exceed the .05 level, except for the showing of discrimination in 1975 against those hired after 1972. As noted above, however, this 1975 finding is skewed by a unique factual circumstance. See Part I-B-1 supra. For every other year the probability that the observed result occurred by chance was less than one in 20; for most years the probability was less than one in a thousand. Id. Similarly, plaintiffs' statistical analyses of grade at entry, evaluations, and discipline all achieved results significant at or above the .05 level. Id. These levels of significance are certainly sufficient to support an inference of discrimination. 102 Plaintiffs' evidence regarding promotions stands on a somewhat different footing. Disparity was demonstrated at a statistically significant level in promotions from GS-11 to GS-12. This evidence suffices to support the requisite inference of discrimination at the GS-11 to GS-12 level. Statistical evidence purporting to show discrimination in promotions above GS-12 did not achieve acceptable levels of statistical significance. Thus, as the trial court correctly found, 508 F.Supp. at 714, statistics alone will not permit an inference of discrimination in promotions to positions above the GS-12 level. 103 Nonetheless, we hold that the District Court correctly found that enough other probative evidence exists to permit an inference of discrimination in promotions above the GS-12 level. In the first place, plaintiffs' evidence regarding promotions above GS-12 was not dispositive either way on the issue of discrimination. Since so few promotions occurred at the higher levels of DEA during the relevant time frame, plaintiffs had to rely on a sample too small to generate statistically significant evidence of discrimination. 508 F.Supp. at 701-702, 714. This lack of statistical proof does not, however, prove that no discrimination took place. And other probative evidence does suggest discrimination. Plaintiffs made a prima facie showing of discrimination in initial grade assignments, work assignments, supervisory evaluations, and discipline. These are precisely the factors that determine a special agent's prospects for discretionary promotions at the higher levels of DEA. See Part I-A supra. With a statistical sample large enough to permit probative results, plaintiffs demonstrated that black agents indeed fared less well in promotions from GS-11 to GS-12, the likely result of discrimination in evaluations, initial grade assignments, work assignments, and discipline. After finding discrimination in the factors that bear most strongly on promotions, and in promotions at the immediately preceding step, the trial court could and did appropriately draw an inference of discrimination in promotions above GS-12. Although indirect, the evidence permits an inference that discrimination was more likely than not. 104 2. The insufficiency of DEA's rebuttal case. DEA also claims that the trial court erred in its evaluation of DEA's case on rebuttal. DEA first points to two errors of law that purportedly skewed the trial court's evaluation of DEA's rebuttal case: (1) the trial court erroneously placed on DEA a burden of persuasion instead of a burden of production, and (2) the trial court erroneously refused to admit into evidence at the remedial stage of the proceeding DEA's alternative regression analyses. On top of these legal errors, DEA claims, the trial court improperly devalued DEA's rebuttal evidence. DEA contends that in light of these errors and the vulnerability of plaintiffs' initial case, the trial court erred in finding discrimination. 105 a. The trial court's allocation of burdens. In a Title VII case alleging disparate treatment the ultimate burden of persuading the trier of fact that the defendant intentionally discriminated against the plaintiff remains at all times with the plaintiff. Burdine, supra, 450 U.S. at 253, 101 S.Ct. at 1093. See Part II-A supra. DEA argues that the trial court violated this precept in analyzing the disparate treatment claim in this case. The controversy turns on the interpretation given the following paragraph in the trial court's opinion: 106 The burden of proof in Title VII litigation always remains on the Plaintiff. After the establishment of a prima facie case, however, the burden of persuasion shifts to the employer. This burden requires the Defendant to articulate some legitimate, nondiscriminatory reason.    If the Defendant meets the rebuttal burden, the Plaintiff has an opportunity to show that the apparently legitimate reason is, in fact, a pretext.    107 508 F.Supp. at 711 (citations omitted). Read literally, one sentence in this passage would seem to indicate that the trial judge erred; he states that a burden of persuasion shifts to the defendant. But read as a whole, the passage indicates that the judge allocated burdens correctly. He states explicitly that the burden of proof always remains with the plaintiff, and the burden that he labels persuasion he defines as one of articulation. 30 108 A clarification that the trial court issued should remove any doubt on this score. The Supreme Court decided Burdine one month after the trial court issued its opinion in this case. Shortly after the Court issued Burdine plaintiffs in this case requested a clarification of the trial court's conclusions of law with regard to the applicable burdens of proof. The court responded that it had allocated burdens in conformity with Burdine. See Order of April 30, 1981, JA 99. 109 This clarification is sufficient reason to distinguish the present case from Freeman v. Lewis, 675 F.2d 398 (D.C.Cir.1982). In Freeman a panel of this circuit held that language almost identical to that of the trial court here was an improper allocation of burdens under Burdine. We question whether that panel gave the trial court's language a wholly fair reading, but we decide that the later clarification in the present controversy suffices to demonstrate that the trial court's language here, though perhaps initially ambiguous, did comport with Burdine's allocation of burdens. 110 b. The decision not to admit DEA's alternative regression analysis. In deciding the liability issues the trial court admonished DEA for failing to substantiate its attack on plaintiffs' statistics by reworking their analysis. 508 F.Supp. at 712. In response DEA sought to introduce at the remedial phase of the trial an alternative regression analysis purporting to demonstrate that race did not explain salary differentials at DEA. Refusing to reopen the question of liability, the trial court rejected this proffer of evidence. See Part I-C-2 & n. 11 supra. 111 DEA argues on appeal as though this rejected evidence were part of the record, see, e.g., brief for appellants at 69-71, but it is not. Nonetheless we must consider whether the trial court properly excluded the evidence. 31 112 In a bifurcated trial the judgment on liability remains interlocutory, and thus subject to the trial court's modification, until the remedial order issues. Marconi Wireless Telegraph Co. v. United States, 320 U.S. 1, 47-48, 63 S.Ct. 1393, 1414-1415, 87 L.Ed. 1731 (1943). This principle applies to bifurcated Title VII actions. Laffey v. Northwest Airlines, Inc., 642 F.2d 578, 584-585 (D.C.Cir.1980). The decision whether to reopen a liability determination is, however, discretionary. On appeal the critical question is whether there was good cause to do so. Absent a convincing showing that the District Court's answer to this question constituted an abuse of discretion, we will not second-guess its decision. Trout v. Lehman, supra, 702 F.2d at 1106. 113 Trout v. Lehman dealt with the precise issue before us in this case. We found that a trial court had not abused its discretion in refusing a defendant's proffer of rebuttal statistics at the remedial phase of the Title VII trial. Two factors underlay the decision: the evidence    could have been discovered and presented at trial by a duly diligent defendant, and the defendants offered no good reason whatsoever to explain why their statistical analyses were not produced at trial. Id. Though the Supreme Court vacated the Trout decision, it did so for reasons wholly unrelated to the question of admissibility of liability evidence at the remedial stage. In fact the Court's remand implicitly approved this circuit's holding that the trial court had not abused its discretion in refusing to admit the evidence; while requiring the District Court to make new factual findings with respect to discrimination, the Supreme Court did not require the District Court to consider the evidence defendant proffered at the remedial stage, or any other new evidence. Lehman v. Trout, supra, --- U.S. at ----, 104 S.Ct. at 1404. 114 In light of the intrinsic strength of the Trout reasoning on this point, and the Court's implicit approval of that reasoning, we follow Trout here. Plaintiffs filed the complaint in this action in January 1977 and the case came to trial in April 1979. DEA made use of statistical experts, and did offer extensive statistical evidence at the liability phase. Without a doubt, DEA had the time and the resources to develop and present its alternative regressions then. And DEA's arguments at the remedial hearing and on appeal contain not a word of justification for its failure to do so. In light of this unjustified omission, the trial court certainly did not abuse its discretion in refusing to admit DEA's alternative regressions. 115 c. The trial court's evaluation of DEA's cohort analysis. Though its regressions were rejected at the remedial stage, DEA did properly introduce during the liability phase a cohort analysis to rebut plaintiffs' showing of disparity. Cohort analysis is another method to test for race discrimination. Under this approach all employees who start together at the same level are surveyed over the course of an observation period and their comparative progress in salary and promotions is evaluated. DEA's expert divided the special agents into 15 cohort groups, each group comprising agents who started in the same year and at the same initial grade level. The analysis revealed discrimination in four of the 15 groups. For purposes of further evaluation, these four groups were broken into subgroups. Discrimination was still present in two of the subgroups. After examining the files of agents in these two subgroups, DEA discovered that three agents had been misclassified. Only when these three agents were excluded did traces of discrimination disappear from the results of the analysis. See Tr. at 1910-1914; Findings p 8, 508 F.Supp. at 697-698. 116 We would overturn the District Court's evaluation of this evidence only if we were to find that evaluation clearly erroneous. Though the District Court may have overstated a bit when it labeled cohort analysis an untried method of statistical study, unsupported in any published statistical work or judicial decision, 508 F.Supp. at 698, the court was surely correct to reject this particular cohort analysis. 117 Courts have viewed cohort analysis in this area with a wary eye, see Valentino, supra, 674 F.2d at 72-73 n. 30; O'Brien v. Sky Chiefs, Inc., 670 F.2d 864 (9th Cir.1982); Trout v. Hidalgo, supra, 517 F.Supp. at 884-885. The flaws that these courts have perceived were perceived in the present case by the District Court. See Findings p 8, 508 F.Supp. at 697-698. The court noted that by comparing those who started at the same grade level, the analysis fails to account for possible discrimination in initial grade assignments, an important allegation in this case. More importantly, the court found that DEA's use of cohort analysis in this case was methodologically flawed. The division of the workforce into extremely small segments made it unlikely that this cohort study would detect disparities. Instead of repeatedly disaggregating until groups were too small to generate any statistically significant evidence of discrimination, DEA's expert should have aggregated the significance of the result in each subgroup to derive a test for significance with respect to the class as a whole. See D. Baldus & J. Cole, supra, at 212 & n. 2. In light of this methodological misstep--and the fact that DEA's analysis tended as much to confirm as to refute the presence of discrimination 32 --the District Court properly discounted the probative value of DEA's rebuttal statistics. 118 3. Weighing the evidence. The analytic application of Title VII's formulaic rules for shifting burdens can come to resemble a furious tennis match. When the volleying is over, however, a Title VII case is like all others: the trier of fact must weigh the plaintiff's proof and the defendant's rebuttal and decide whether plaintiffs have met the ultimate burden of persuasion that the law imposes on them. See U.S. Postal Service Bd. of Gov. v. Aikens, 460 U.S. 711, 716, 103 S.Ct. 1478, 1482, 75 L.Ed.2d 403 (1983). We have already evaluated DEA's challenges to the particulars that went into the District Court's balance in this case. Since we have found no errors of law or clearly erroneous findings, all that remains is to examine the court's overall assessment of the evidence. We review with deference. Only if we find the trial court's ultimate decision to be clearly erroneous will we overturn it. Albemarle Paper Co., supra, 422 U.S. at 424, 95 S.Ct. at 2374. 119 Plaintiffs brought in a battery of statistics to prove discrimination at DEA. Their analyses tended to show significant salary disparities between comparably qualified white and black special agents, and discrimination in DEA's initial grade assignments, work assignments, supervisory evaluations, promotions, and imposition of discipline. In response DEA sought primarily to cast sufficient doubt on the existence of race-related disparities to prevent plaintiffs from carrying their burden of persuasion. 120 To do so DEA argued that plaintiffs were required to show gross disparities because they had failed to produce any credited individual anecdotal accounts of discrimination. We have held that, as a matter of law, plaintiffs were not required to meet this enhanced threshold of gross disparities. See Part II-B-1-b-i supra. DEA also argued that plaintiffs' salary regressions had failed to show actionable disparities at levels of statistical significance sufficient to permit an inference of discrimination. We have held that the District Court properly found that the studies did show actionable disparities at sufficient levels of statistical significance. See Part II-B-1-b-ii supra. In any event, this objection went only to plaintiffs' salary regressions and thus failed to rebut the showings of discrimination in initial grade assignments, work assignments, supervisory evaluations, promotions, and imposition of discipline. The keystone of DEA's defense was the argument that plaintiffs had failed to account for the explanatory variable of prior law enforcement experience. In essence DEA has argued that this variable, not race, explains virtually all of the observed disparities between white and black special agents. DEA styled this argument primarily as an attack on the sufficiency of plaintiffs' prima facie case. In other words, DEA has argued that because plaintiffs failed to account for this factor their initial offer of proof was insufficient to support an inference of discrimination. We have held that plaintiffs' failure to account explicitly for this variable was not fatal to its prima facie case; the trial court properly found that the evidence plaintiffs did present was sufficient, notwithstanding this omission, to support an inference of discrimination under the functional test of Teamsters, Furnco, and Burdine. See Part II-B-1-a supra. 121 Even if this argument is insufficient to invalidate plaintiffs' prima facie case, it might nonetheless serve as a legitimate nondiscriminatory explanation for the observed disparities between white and black agents. In other words, even if plaintiffs' omission did not preclude them as a matter of law from making their initial case, DEA's explanation might serve to preclude the ultimate inference of discrimination against black agents under the disparate treatment theory. Claiming that this factor, not race, explains the disparities, DEA has in effect made such an argument. To rebut plaintiffs' disparate treatment claim DEA need not carry the burden of persuasion as to this legitimate nondiscriminatory explanation. See Burdine, supra, 450 U.S. at 253-254, 101 S.Ct. at 1093-1094. The evidence must, however, cast sufficient doubt on plaintiffs' case to cause the trier of fact not to draw the ultimate inference of discrimination. See Part II-A-1 supra. 122 The District Court did not find this rebuttal sufficiently strong to preclude the ultimate inference of discrimination. On review we cannot say that the court erred in this assessment. DEA has introduced no admissible evidence that this alleged differential in prior law enforcement experience exists. As we have noted, there is no reason to assume that black agents in a group with one year of prior criminal investigative experience are more likely than white agents in that group to lack a second year of such experience. See Part II-B-1-a supra. Nor has DEA presented any admissible evidence that the purported differential in law enforcement experience explains the observed disparities. 123 Absent such evidence, we are left, as the trial court noted, with mere speculation and conjecture. See 508 F.Supp. at 712. Of course, the most effective way to rebut a prima facie case is to present more accurate statistics. Trout v. Lehman, supra, 702 F.2d at 1102. A defendant is not absolutely required to rework a plaintiffs' statistics when, as in this case, the omitted variable was allegedly too subjective to admit of quantification. 33 A defendant must, however, make some credible showing that the omission skewed plaintiffs' statistics. At a minimum the employer must raise a genuine issue of fact as to the veracity of plaintiffs' proof, and [t]o accomplish this, the defendant must clearly set forth, through the introduction of admissible evidence, the reasons for the observed disparity. Burdine, supra, 450 U.S. at 254255, 101 S.Ct. at 1094. Thus the defendant cannot meet its burden merely through    argument of counsel. Id. at 255 n.9, 101 S.Ct. at 1094 n. 9. Because DEA has introduced no evidence to support its purported nondiscriminatory explanation, this rebuttal fails as a matter of law. 124 On balance, we find no reversible error in the District Court's overall assessment of the evidence. The court properly attributed probative weight to plaintiffs' statistical analyses, and properly rejected the three aspects of DEA's case on rebuttal--the need for gross disparities, the insufficiency of the statistical studies, and the purported failure to account for prior law enforcement experience. In light of these findings, the court appropriately held that DEA had engaged in a pattern or practice of discrimination against black special agents, 508 F.Supp. at 712, and properly held that DEA's initial grade assignments, work assignments, supervisory evaluations, imposition of discipline, and promotion process had disparate impacts on black agents. Id. at 712-715. 34 We therefore affirm the District Court's liability determination in its entirety. 125 4. Disparate impact analysis of DEA's rebuttal evidence. We note finally that even had DEA succeeded in rebutting plaintiffs' disparate treatment case by making a credible showing that the differential in prior law enforcement experience explained the observed disparity, DEA would have done no more than create a situation ripe for resolution under the disparate impact theory. See Part II-A-1-b supra. According to DEA's argument, black special agents appear to do less well throughout the range of DEA's employment system because they tend to start lower in that system as a result of their relative lack of more than one year of prior law enforcement experience. This boils down to a claim that DEA's requirement of a second year of law enforcement experience for entry at GS-9 instead of GS-7 has an adverse impact on blacks because they tend to lack that qualification. Between plaintiffs' and defendants' proof, the trier of fact would have had before it all the elements of a traditional disparate impact claim: plaintiffs had shown a disparity and defendant had pinpointed the facially neutral employment practice causing the disparity. In this situation the trial court would properly have applied the disparate impact analysis of Griggs, supra, and its progeny. Had DEA made a credible showing that the requirement of an additional year of law enforcement experience caused the disparity, DEA would have been required to show the job-relatedness of such a requirement. Griggs, supra, 424 U.S. at 432, 91 S.Ct. at 854; Albemarle Paper Co., supra, 422 U.S. at 425, 95 S.Ct. at 2375. DEA has not even attempted any such showing. Thus, even had DEA succeeded in its attempt to articulate a legitimate nondiscriminatory explanation, DEA would still have been found in violation of Title VII under the disparate impact theory.