Offense Categories and Classes


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Offense Categories and Classes

To examine disproportionality in the intersection of offense seriousness and offense type, proportionality ratios were calculated (PRs). This calculation takes the ratio of the proportion of arrests, detainments, or incarcerations for a specific offense class within each offense category for each gender. To obtain further explanation of these calculations, please see Appendix C. Similar to the relative rate ratio, a PR of 1 indicates equal proportional representation. A PR below 1 indicates an under-representation of girls. As with the RRR, available data do not allow for an individual to be linked across different stages and the PR for each stage must be interpreted independent of the other stages. Reporting misdemeanor arrests for juveniles to CHRI by law enforcement is voluntary. As a result, arrest offense class disparities are a conservative estimate.

The girls' proportion of arrests and commitments to corrections for misdemeanor offenses was higher for all offense categories except noncompliance offenses.

Girls' arrests and commitments to corrections were more likely to be for misdemeanor property offenses than boys. In 2007, girls' arrests were 22 percent more likely to be for misdemeanor property offenses and in FY04, girls' commitments to corrections were almost 119 percent more likely to be for misdemeanor property offenses than boys.

Girls' arrests and commitments to corrections were also more likely to be for misdemeanor person offenses. In 2007, girls' arrests were 16 percent more likely to be for misdemeanor person offenses and in FY04, their commitments to corrections were 136 percent more likely to be for misdemeanor person offenses than boys'.

Girls' arrests were 17 percent more likely than boys' to be for felony noncompliance offenses, although their commitments to corrections were 17 percent less likely to be for felony noncompliance offenses. However, girls' commitments to corrections were 15 percent more likely to be for misdemeanor noncompliance offenses.

Table 20 shows the summary of the proportionality ratios for girls by offense category and class for arrests and commitments to corrections. For additional tables on these calculations, please see Appendix D. It is important to note that arrest and commitment PRs must be interpreted independent of one another.

Table 20
Summary of girls' proportion ratios for arrests and IDOC commitments by offense class and category, 2007*

Arrest proportion ratios (PR) Corrections proportion ratios (PR)
Offense Category Misdemeanor Felony Other/Unknown Misdemeanor Felony Other/Unknown
Person 1.16 0.65 - 2.36 0.72 -
Sex 2.86 0.18 - - - -
Weapons 1.67 0.56 - 10.70** 0.52 -
Property 1.22 0.66 0.2 2.19 0.8 -
Drugs 1.43 0.69 5.31 6.98** 0.64 -
Noncompliance 0.92 1.17 1.2 1.15 0.83 -
Status 0.97 - 1.05 1 - -
Other 1.87 1.15 0.95 3.33** 0.74 -

Source: Authority's CHRI Ad Hoc datasets, Illinois Department of Corrections
* Corrections data for 2005 through 2007 were unavailable; 2004 was used
** As the number of girls committed to IDOC for drug, weapons, or "other" offenses in FY04 was small, this ratio may be inflated.

Statistical Tests of Differences in Proportions between Girls and Boys

While our data show that girls' arrests, admissions to detention, and commitments to corrections are more often for less serious offenses than boys, statistical analyses were used to determine if these differences were meaningful. With such large sample sizes, Chi-square analyses showed significant associations between gender and class, but subsequent phi and phi-square analyses showed these associations to be substantively weak. A test of the difference in proportions was used to determine if the proportion of girls' arrests or commitments to corrections for misdemeanor offenses was significantly higher than the proportion of boys' arrests or commitments to corrections for misdemeanor offenses.