What is the disparate impact cause of action under section 703(a)(2)?

The disparate impact cause of action developed out of the language in section 703(a)(2) prohibiting discrimination based on deprivation of employment opportunities, such as the opportunity to be hired or promoted. See, e.g., Connecticut v. Teal, 457 U.S. 440, 448-50, 102 S.Ct. 2525, 2531-32, 73 L.Ed.2d 130 (1981). Our court's disparate impact cases fall squarely within the language of section 703(a)(2). The cases in which we have concluded that the plaintiff has proved discrimination based on a disparate impact theory have all involved plaintiffs who claimed that they were denied employment opportunities as the result of artificial, arbitrary, and unnecessary barriers that excluded members of a protected group from being hired or promoted, see, e.g., Bouman v. Block, 940 F.2d 1211, 1224-26 (9th Cir.), cert. denied, --- U.S. ----, 112 S.Ct. 640, 116 L.Ed.2d 658 (1991), not plaintiffs contending that they were subjected to harsher working conditions than the general employee population.