elevant comparison is between the percentage of minority employees and the percentage of potential minority applicants in the qualified labor pool." Carter v. Ball, 33 F.3d 450, 456 (4th Cir. 1994); see also City of Richmond v. J.A. Croson Co., 488 U.S. 469, 501-02, 109 S. Ct. 706, 102 L. Ed. 2d 854 (1989); Mc