Statistical Analyses


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Statistical analyses

Various statistical analyses were performed in this report. Chi-Square, phi, phi-square, and Yule's Q analyses were used for person and property offenses. The results of these analyses are presented in the corresponding offense category sections of this report.

Additional analyses were done to examine the difference in proportions of offense category and misdemeanor and felony justice system involvement. Explanations of and results from these analyses are presented in the section on girls' disproportionality.

Arrests

Girls were arrested less often than boys, for less serious offenses, and experienced a greater increase in arrest rates.

In Illinois, girls were arrested less often than boys, coinciding with national findings that girls have less involvement in the juvenile justice system.(13) Additionally, girls were arrested less often for serious offenses than boys, also in accordance with national trends.(14)

In 2007, there were 48,032 arrests made of youth between the ages of 10 and 16 in Illinois. The gender in 12 arrests was not recorded (0.02 percent). Of the remaining 48,020 arrests, 78 percent were boys (n=37,472) and 22 percent were girls (n=10,548).

In 2007, the girls' rate of arrest was 1,690 for every 100,000 girls age 10 to 16, and the boys' rate was 5,740. From 2002 to 2007, girls' rates of arrest increased 9 percent, compared to a 6 percent increase for boys. Figure 13 shows the rate of juvenile arrests for boys and girls from 2002 to 2007.

Figure 13
Rate of juvenile arrests by gender, 2002-2007

Line Chart: 2 line chart (Boys & Girls) Rate of arrests per 100,000 ages 10-16

2002 2003 2004 2005 2006 2007
Boys ~5,400 ~5,400 ~5,450 ~6,000 ~5,850 5,740
Girls ~1,500 ~1,500 ~1,550 ~1,600 ~1,600 1,690

Source: Authority's CHRI Ad Hoc datasets

Girls' arrests were more likely than boys' arrests to be for less serious offenses. In 2007, girls had a higher proportion of their arrests for misdemeanors (n=6,978 or 66 percent) than boys (n=20,400 or 54 percent). Conversely, felony offense arrests were higher for boys (n=12,052 or 32 percent) than girls (n=1,964 or 19 percent).

Reporting misdemeanor arrests for juveniles to CHRI by law enforcement is voluntary. As a result, arrest offense class disparities are a conservative estimate.

Detention

Girls were admitted to detention less often than boys and experienced a greater decrease in detention rates.

From 2002 to 2007 in Illinois, girls were detained less often than boys. While both boys' and girls' rates of admissions to detention decreased, girls experienced a larger decrease in admissions rates.

Girls' detention rates decreased 20 percent between 2002 and 2007, while the boys' rates decreased 9 percent. Figure 14 shows the rate of detention admissions from 2002 to 2007 by gender.

In 2007, 17 percent of the 15,747 juveniles detained were girls (n=2,677). Girls were detained at a rate of 437 for every 100,000 girls ages 10 to 16. Boys were detained at a rate of 2,036 for every 100,000 boys in that age group.

Figure 14
Rate of juvenile admissions to secure detention by gender, 2002-2007

Line Chart: 2 line chart (Boys & Girls) Rate of admissions per 100,000 ages 10-16

2002 2003 2004 2005 2006 2007
Boys ~2,130 ~2,050 ~2,075 ~2,130 ~2,150 2,036
Girls ~550 ~500 ~490 ~480 ~475 437

Source: Juvenile Monitoring Information System

Corrections

Girls were committed to corrections less often than boys and their commitments were for less serious offenses.

Girls were committed to corrections less often than boys. In FY04, the last year for which data were available, 11 percent of the 1,729 juveniles committed to IDOC for new offenses were girls (n=193). Girls were also incarcerated at a rate much lower than boys. In FY04, 54 girls were committed to IDOC for every 100,000 girls age 13 to 16, while boys were committed at a rate of 406.

Although incarceration rates decreased overall for juveniles, during the time period examined girls experienced a smaller decrease in their rates of incarceration than boys. The girls' rate of commitment decreased 17 percent from 65 in FY99 to 54 in FY04. During this same time period, the boys' rate decreased 29 percent. Figure 15 shows the rate of juvenile commitments to corrections by gender from FY99 to FY04.

Figure 15
Rate of juvenile commitments to IDOC by gender, FY99-FY04

Line Chart: 2 line chart (Boys & Girls) Rate of admissions per 100,000 ages 13-16

1999 2000 2001 2002 2003 2004
Boys ~550 ~460 ~410 ~420 ~415 406
Girls 65 ~65 ~65 ~54 ~54 54

Source: Juvenile Monitoring Information System

Girls had a larger proportion of commitments for misdemeanor offenses than boys. In FY04, 38 percent of girls' commitments (n=73) and 14 percent of boys' commitments (n=218) were for misdemeanors. Conversely, 62 percent of girls' commitments (n=120) and 86 percent of boys' (n=1,317) were for felonies.


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