Adverse Impact Analysis / Four-Fifths Rule
Typically, adverse impact is determined by using the four-fifths or eighty percent rule. The four-fifths or 80% rule is described by the guidelines as “a selection rate for any race, sex, or ethnic group which is less than four-fifths (or 80%) of the rate for the group with the highest rate will generally be regarded by the Federal enforcement agencies as evidence of adverse impact, while a greater than four-fifths rate will generally not be regarded by Federal enforcement agencies as evidence of adverse impact.”