Just a guess: more white females than black females go to college, where they have plenty of opportunities for underage drinking, marijuana use, trespassing, vandalism, or other minor crimes. More black women at that age are mothers, where they have to provide for their kid and don't have time to get into mischief.
The arrest rates at age 18 were nearly identical for white vs. black females, the discrepancy only arose in ages 18-23. It would be interesting to see the data broken out by crime and by educational achievement.
Just a guess: more white females than black females go to college,
In terms of raw numbers, yes, because there are more white females than black females in the U.S. In terms of rates, no, black women enroll in college at a higher rate than white women [0] and are awarded degrees at a higher rate than white women [1]. Now this is a relatively recent (last 10 years) development so it could be that arrest rates haven't had time to adjust for this if the hypothesis is correct.
[0] http://www.census.gov/hhes/school/data/cps/2011/tables.html look at the "White alone non-Hispanic" and "Black alone" table data and assuming we're limiting the comparison to 18-24 yro per the post I'm responding to, 4.6% of black women attend college vs 4.3% of white women.
The arrest rates at age 18 were nearly identical for white vs. black females, the discrepancy only arose in ages 18-23. It would be interesting to see the data broken out by crime and by educational achievement.