In December 2010, the Florida Advisory Committee to the United States Commission on Civil Rights issued a report titled “School Discipline in Florida: Discipline Disparities Leave Many Children Behind.”Figure 2 of the report (at 11) was titled “The widening racial disparity in discipline despite reductions in out-of-school suspensions.”The figure showed that between 2008 and 2010, a period during which (the report explained) there were substantial general reductions in suspensions, the black proportion of total suspensions increased from 71.82 percent to 73.14 percent, while the white proportion of total suspensions decreased from 20.36% to 19.50%.A corollary to the pattern whereby general declines in an outcome tend to cause increased relative differences in experiencing the outcome is a pattern whereby general declines in an outcome tend to increase the proportion the more susceptible group comprise of persons experiencing the outcome.Thus, unless there was a substantial increase in the proportion blacks comprised of total students, the relative difference in suspension rates increased (as one with a sound statistical background would expect). See both both “Race and Mortality,” Society (Jan./Feb. 2000), and “Race and Mortality Revisited,” Society (July/Aug. 2014), regarding the ways observers note that increases in relative differences occurred “despite” general reductions without recognizing reasons to believe that the increase in relative differences occurred “because of” general reductions.
Two other aspect of the report warrant note. First, to measure disparities the report relied on what it termed the “disparity index,” which is the ratio of the proportion the group comprises of students experiencing an outcome to the proportion it comprises of total students. The problems with that measure, apart from the fact that general reductions in discipline tend to increase the ratio for groups with higher discipline rates, are addressed on the IDEA Data Center Disproportionality Guide subpage of the Discipline Disparities page (with regard to the method described identified as (d), though the reader should be mindful that method (d) employs the relative difference, which is disparity index value minus 1).The problems are also illustrated in slides 55 to 59 of the January 20, 2015 University of California, Irvine methods workshop titled “The Mismeasure of Discrimination.”
Second, at page 12, the report notes that as disciplinary consequences grow more severe, racial disproportionality increases.Such points are commonly made in the discussion of discipline disparities or disparities in the criminal justice system.But those making them virtually never recognize the one will find relative differences in rates of experiencing adverse outcome will tend almost invariably to increase (while relative difference in avoiding the outcome will tend almost invariably to decrease) as the outcome grow less common (are restricted toward the tail of the distributions), while relative differences in avoiding the .Consequently, inferences based on these patterns have rarely, if ever, been sound.See "Race and Mortality Revisited." See also “Mired in Numbers,” Legal Times (Oct. 12, 1996).