Evaluating Disproportionate Impact


Using cohorts and outcomes from the California Community Colleges Chancellor’s Office (CCCCO) Student Success Scorecard and DataMart, this document presents two methodologies to measure disproportional impact for disaggregated subgroups within the California Community Colleges (CCC) student population: the 80% test and the proportionality test.

Disproportionate impact occurs when “the percentage of persons from a particular racial, ethnic, gender, age or disability group who are directed to a particular service or placement based on an assessment instrument, method, or procedure is significantly different from the representation of that group in the population of persons being assessed, and that discrepancy is not justified by empirical evidence demonstrating that the assessment instrument, method or procedure is a valid and reliable predictor of performance in the relevant educational setting.”  [Title 5 Section 55502(d)]

The second-to-last column of all tables disaggregated by cohort student characteristics contains an evaluation of possible disproportionate impact for each subgroup of students using the “80% Rule” outlined in the 1978 Uniform Guidelines on Employee Selection Procedures and was used in Title VII enforcement by the U.S. Equal Opportunity Commission, Department of Labor, and the Department of Justice.

The 80% Rule states that: “A selection rate for any race, sex, or ethnic group which is less than four-fifths (4/5) (or eighty percent) 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.” [Section 60-3, Uniform Guidelines on Employee Selection Procedure (1978); 43 FR 38295(August 25, 1978)]

Subgroups that do not comprise at least two percent of the cohort are denoted by with an asterisk (*). The bold percentage located at the bottom of the disproportionate impact column provides the outcome percentage of the reference group multiplied by 80 percent (the reference group is provided in parentheses).

The last column of all tables contains the results obtained from the proportionality methodology. The proportionality methodology compares the percentage of a disaggregated subgroup in an initial cohort to its own percentage in the resultant outcome group. The formula for proportionality is the percentage in the outcome group divided by the percentage in the original cohort (outcome percentage/cohort percentage). For example, 7.9 percent of the first-time, “degree/transfer-seeking” cohort is comprised of African American or black students; whereas 6.0 percent of the students who achieved a successful outcome (i.e., degree, certificate, transfer, or transfer-prepared) were African American or black students. Dividing 6.0% by 7.9% we find a proportionality index of 0.76. The higher the proportionality, the higher the rate at which a subgroup has attained a desired educational outcome; the lower the proportionality index, the lower the attainment rate.

The proportionality methodology does not specify at which point a proportionality index should be considered as a “disproportionate impact.” The designation of which disaggregated subgroups should be considered as disproportionately impacted will rely on the judgment of the analysis team at the college.

Proportionality Index



Proportions of subgroups are equal.

Less Than 1.0

Subgroup is less prevalent in the   outcome group.

More Than 1.0

Subgroup is more prevalent in the   outcome group.


The tables below summarize the indicators of possible disproportionate impact by the different population groups of students across all measures investigated in this report. The summary categories are defined as: