Adverse impact takes place when an employment decision, practice, or policy has a disproportionately negative effect on a protected group. HR professionals rely on the "four-fifths" or "80 percent" rule to judge whether adverse impact may have occurred. Consider the following two situations:

(a) The selection rate for females:

(b) The selection rate for males:

SexTotal ApplicantsSelected ApplicantsSelection RateFemale1100700Male1050850Total2,1501,550