Four Fifths Rule

Four Fifths Rule is a simple statistical guideline used to detect potential adverse impact in employment decisions. The rule compares selection rates between groups to flag possible discrimination. HR teams use the Four Fifths Rule when reviewing hiring, promotion, or layoff outcomes.

What is Four Fifths Rule

The Four Fifths Rule states that a protected group's selection rate should be at least 80 percent of the rate for the group with the highest selection rate. It is not a legal test by itself, but it signals when deeper analysis is needed.

How Does it Work

Selection rate of group A ÷ selection rate of group B should be at least 0.8 or 80 percent

If the ratio falls below 80 percent, HR should investigate whether selection procedures, job requirements, or bias are causing the disparity.

Practical Usage

HR professionals and hiring managers use the rule as an initial compliance check. Typical scenarios include:

• Reviewing candidate screening and interview outcomes after a hiring round
• Assessing promotion or layoff decisions for disparate impact
• Triggering further statistical or legal review when disparities appear

Examples and Use Cases

Example: If 50 percent of male applicants are hired and 35 percent of female applicants are hired, the female selection rate is 70 percent of the male rate and triggers further review.

Related HR Concepts

Related terms include adverse impact, disparate impact, selection rate, affirmative action, and employment law compliance. These concepts guide deeper analysis beyond the Four Fifths Rule.