In United States employment law, the doctrine of disparate impact holds that employment practices may be considered discriminatory and illegal if they have a disproportionate "adverse impact" on persons along the lines of a protected trait. Although the protected traits vary by statute, most federal civil rights laws include race, color, religion, national origin, and gender as protected traits, and some laws include disability status and other traits as well.
Under the doctrine, a violation of Title VII of the 1964 Civil Rights Act may be proven by showing that an employment practice or policy has a disproportionately adverse effect on members of the protected class as compared with non-members of the protected class. Therefore, the disparate impact doctrine under Title VII prohibits employers "from using a facially neutral employment practice that has an unjustified adverse impact on members of a protected class. A facially neutral employment practice is one that does not appear to be discriminatory on its face; rather it is one that is discriminatory in its application or effect." Where a disparate impact is shown, the plaintiff can prevail without the necessity of showing intentional discrimination unless the defendant employer demonstrates that the practice or policy in question has a demonstrable relationship to the requirements of the job in question. This is the "business necessity" defense.
In addition to Title VII, other federal laws also have disparate impact provisions, including the Age Discrimination in Employment Act of 1967. Some civil rights laws, such as Title VI of the Civil Rights Act of 1964, do not contain disparate impact provisions. The U.S. Supreme Court has not yet resolved whether the Fair Housing Act of 1968 creates a cause of action for disparate impact.
Disparate impact contrasts with disparate treatment. A disparate impact is unintentional, whereas a disparate treatment is an intentional decision to treat people differently based on their race or other protected characteristics. The disparate impact doctrine is controversial because it can require persons to intentionally discriminate against one group in order to avoid creating a disparate impact on another group, and that intentional discrimination can amount to illegal disparate treatment or a violation of the U.S. Constitution's guarantee of equal protection.
While disparate impact is a legal theory of liability under Title VII, adverse impact is one element of that doctrine, which measures the effect an employment practice has on a class protected by Title VII. In the Uniform Guidelines on Employee Selection Procedures, an adverse impact is defined as a "substantially different rate of selection in hiring, promotion, or other employment decision which works to the disadvantage of members of a race, sex, or ethnic group.". A "substantially different" rate is typically defined in government enforcement or Title VII litigation settings using the 80% Rule, statistical significance tests, and/or practical significance tests. Adverse impact is often used interchangeably with "disparate impact," which was a legal term coined in one of the most significant U.S. Supreme Court rulings on disparate or adverse impact: Griggs v. Duke Power Co., 1971. Adverse Impact does not mean that an individual in a majority group is given preference over a minority group. However, having adverse impact does mean that there is the “potential” for discrimination in the hiring process and it could warrant investigation.
The 80% rule
The 80% test was originally framed by a panel of 32 professionals (called the Technical Advisory Committee on Testing, or TACT) assembled by the State of California Fair Employment Practice Commission (FEPC) in 1971, which published the State of California Guidelines on Employee Selection Procedures in October, 1972. This was the first official government document that listed the 80% test in the context of adverse impact, and was later codified in the 1978 Uniform Guidelines on Employee Selection Procedures, a document used by the U.S. Equal Employment Opportunity Commission (EEOC), Department of Labor, and Department of Justice in Title VII enforcement.
Originally, the Uniform Guidelines on Employee Selection Procedures provided a simple "80 percent" rule for determining that a company's selection system was having an "adverse impact" on a minority group. The rule was based on the rates at which job applicants were hired. For example, if XYZ Company hired 50 percent of the men applying for work in a predominantly male occupation while hiring only 20 percent of the female applicants, one could look at the ratio of those two hiring rates to judge whether there might be a discrimination problem. The ratio of 20:50 means that the rate of hiring for female applicants is only 40 percent of the rate of hiring for male applicants. That is, 20 divided by 50 equals 0.40, which is equivalent to 40 percent. Clearly, 40 percent is well below the 80 percent that was arbitrarily set as an acceptable difference in hiring rates. Therefore, in this example, XYZ Company could have been called upon to prove that there was a legitimate reason for hiring men at a rate so much higher than the rate of hiring women. Since the 1980s, courts in the U.S. have questioned the arbitrary nature of the 80 percent rule, making the rule less important than it was when the Uniform Guidelines were first published. A recent memorandum from the U.S. Equal Employment Opportunities Commission suggests that a more defensible standard would be based on comparing a company's hiring rate of a particular group with the rate that would occur if the company simply selected people at random. In other words, if a company's selection system made it statistically more difficult than pure chance for a member of a certain group, such as women or African-Americans, to get a job, then this could be reasonably viewed as evidence that the selection system was systematically screening out members of that social group.
More advanced testing
The concept of practical significance for adverse impact was first introduced by Section 4D of the Uniform Guidelines, which states "Smaller differences in selection rate may nevertheless constitute adverse impact, where they are significant in both statistical and practical terms …" Several federal court cases have applied practical significance tests to adverse impact analyses to assess the "practicality" or "stability" of the results. This is typically done by evaluating the change to the statistical significance tests after hypothetically changing focal group members selection status from "failing" to "passing" (see for example, Contreras v. City of Los Angeles (656 F.2d 1267, 9th Cir. 1981); U.S. v. Commonwealth of Virginia (569 F.2d 1300, 4th Cir. 1978); and Waisome v. Port Authority (948 F.2d 1370, 1376, 2d Cir. 1991)).
This form of discrimination occurs where an employer does not intend to discriminate; to the contrary, it occurs when identical standards or procedures are applied to everyone, despite the fact that they lead to a substantial difference in employment outcomes for the members of a particular group and they are unrelated to successful job performance. An important thing to note is that disparate impact is not, in and of itself, illegal. This is because disparate impact only becomes illegal if the employer cannot justify the employment practice causing the adverse impact as a "job related for the position in question and consistent with business necessity" (called the "business necessity defense").
For example, a fire department requiring applicants to carry a 100 lb (50 kg) pack up three flights of stairs. The upper-body strength required typically has an adverse impact on women. The fire department would have to show that this requirement is necessary and job-related. This typically requires employers to conduct validation studies that address both the Uniform Guidelines and professional standards. Accordingly, a fire department could be liable for "discriminating" against female job applicants solely because it failed to prove to a court's satisfaction that the 100-pound requirement was "necessary," even though the department never intended to hinder women's ability to become firefighters.
Disparate impact is not the same as disparate treatment. Disparate treatment refers to the "intentional" discrimination of certain people groups during the hiring, promoting or placement process.
The Fair Housing Act
The disparate impact theory has application also in the housing context under Title VIII of the Civil Rights Act of 1968, also known as The Fair Housing Act,. The ten federal appellate courts that have addressed the issue have all determined that one may establish a Fair Housing Act violation through the disparate impact theory of liability. The U.S. Department of Housing and Urban Development's Office of Fair Housing and Equal Opportunity, the federal government which administers the Fair Housing Act, issued a proposed regulation on November 16, 2011 setting forth how HUD applies disparate impact in Fair Housing Act cases. On February 8, 2013, HUD issued its Final Rule .
The U.S. Supreme Court has not yet determined whether the Fair Housing Act contains a disparate impact provision. This question reached the Supreme Court twice since 2012, first in Magner v. Gallagher and then in Township of Mount Holly v. Mount Holly Gardens Citizens. The Supreme Court seemed likely to rule that the Act does not contain a disparate impact provision, but both cases settled before the Court could issue a decision. The federal government appeared to pressure the settlement in one or both cases in an effort to preserve the disparate impact doctrine.
The disparate impact doctrine of liability is controversial for several reasons. First, the doctrine labels certain unintended effects as "discriminatory," although discrimination is an intentional act. Second, the doctrine is in tension with disparate treatment provisions under civil rights laws as well as the U.S. Constitution's guarantee of equal protection. For example, if the hypothetical fire department discussed above used the 100-pound requirement, that policy might disproportionately exclude female job applicants from employment. Under the 80% rule mentioned above, unsuccessful female job applicants would have a prima facie case of disparate impact "discrimination" against the department if they passed the 100-pound test at a rate less than 80% of the rate at which men passed the test. In order to avoid a lawsuit by the female job applicants, the department might refuse to hire anyone from its applicant pool -- in other words, the department may refuse to hire anyone because too many of the successful job applicants were male. Thus, the employer would have intentionally discriminated against the successful male job applicants because of their gender, and that likely amounts to illegal disparate treatment and a violation of the Constitution's right to equal protection. In the 2009 case Ricci v. DeStefano, the U.S. Supreme Court ruled that a fire department committed illegal disparate treatment by refusing to promote mostly white firefighters in an effort to avoid disparate impact liability in a potential lawsuit by black and Hispanic firefighters who disproportionately failed tests for job promotions. Although the Court in that case did not reach the constitutional issue, Justice Scalia's concurring opinion suggested the fire department also violated the constitutional right to equal protection. Even before Ricci, lower federal courts have ruled that actions taken to avoid potential disparate impact liability violate the constitutional right to equal protection. One such case is Biondo v. City of Chicago, Illinois, from the Seventh Circuit.
The disparate impact doctrine is especially controversial under the Fair Housing Act because the Act regulates many activities relating to housing, insurance, and mortgage loans -- and some scholars have argued that the doctrine's use under the Fair Housing Act contributed to the crash of the U.S. housing market and ensuing global economic recession.
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- E.g. Griggs v. Duke Power Co., 401 U.S. 424, 91 S. Ct. 849, 28 L. Ed. 2d 158 (1977)
- Smith v. City of Jackson, Mississippi, 544 U.S. 228 (2005), http://www.law.cornell.edu/supct/html/03-1160.ZS.html
- Alexander v. Sandoval, 532 U.S. 275 (2001), http://www.law.cornell.edu/supct/html/99-1908.ZS.html
- "Uniform guidelines on employee selection procedures". uniformguidelines.com. Retrieved November 14, 2007. "Adverse impact. ”A substantially different rate of selection in hiring, promotion, or other employment decision which works to the disadvantage of members of a race, sex, or ethnic group. See section 4 of these guidelines."
- Lawrence Ph.D., Amie (May 31, 2011). "The Big AI". Select International, Inc.. Retrieved May 31st, 2011.
- Dan Biddle. Adverse Impact And Test Validation: A Practitioner's Guide to Valid And Defensible Employment Testing. Aldershot, Hants, England: Gower Technical Press. pp. 2–5. ISBN 0-566-08778-2.
- "Adverse impact and the "four-fifths rule."". uniformguidelines.com. Retrieved November 14, 2007. "Smaller differences in selection rate may nevertheless constitute adverse impact, where they are significant in both statistical and practical terms"
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- 1964/1991 Civil Rights Act, Section 2000e-2[k]  [A]