Federal fair employment laws protect employees from discrimination on the basis of age, race, color, gender, national origin, religion, and disability. Federal law covers employers of 15 or more, except for the Age Discrimination in Employment Act (ADEA), which covers employers with 20 or more employees. State laws often cover employers with fewer employees and provide protection for groups not covered under federal law. Certain individuals in the workplace, such as independent contractors, are not protected by federal fair employment laws if they are not employees. Employers are liable for discriminatory acts by supervisors--in some cases, strictly liable. There are many preventive measures an employer can take to reduce the probability of being sued for discrimination. Civil rights laws also impose numerous recordkeeping requirements on employers.