Number: II.11.A. 
Date Issued: Dec, 1993
Date Revised: Sept.1999


To conduct statistical review of activities of the examination and selection process to determine adverse impact against federally protected groups.


  1. Adverse impact is a substantially different rate of selection in hiring, promotion, or other employment decision which works to the disadvantage of members of protected groups. A substantially different rate of selection is determined by the 4/5ths or 80% Rule developed and published through the Equal Employment Opportunity Commission (EEOC) Guidelines.

  2. For Santa Cruz County, the following comparisons of protected groups are made:

    1. Black, Hispanic, Asian and American Indian selection rates compared to White selection rates.

    2. Female selection rates compared to male selection rates.

  3. he County uses a computerized applicant tracking system (TRAC) to perform computations for the rate of application; determination of minimum qualifications; completion of tests and hiring rates. These computations are reviewed by Personnel Services Division and Equal Employment Opportunity Division staff to determine problems and improve these processes for all applicants.

  4. n making comparisons, the ideal candidate pool for statistical significance is 200. Numbers below 50 do not characterize statistical significance and should be reviewed with care as to drawing conclusions.


Adverse impact is determined by a four step process outlined below:

  1. Calculate the rate of selection for each group (divide the number of persons selected from a group by the number of applicants from that group).

  2. Observe which group has the highest selection rate. Is this group also the majority group (white or male)? If it is proceed with the analysis. If it is not, proceed with the analysis taking care to analyze whether the impact is adverse to protected groups. 

  3. Calculate the impact ratios, by comparing the selection rate for each group with that of the highest group (divide the selection rate for a group by the selection rate for the highest group).

  4. Observe whether the selection rate for any group is substantially less (i.e. usually less that 4/5ths or 80%) than the selection rate for the highest group. If it is, adverse impact is indicated in most circumstances.

    Example: If there are 80 white applicants and 48 are hired there is a 60% selection rate for whites. If there are 40 black applicants and 12 are hired, this gives a 30% selection rate for blacks. A comparison of the black selection rate (30%) with the white selection rate (60%) shows that the black rate is 30/60 or 50% of the white rate. Since 50% is less that the 4/5 (80%) rule of thumb, adverse impact is indicated.