Answer: It's primarily explained by our city's history of systemic racism. A large portion of Chicago's population are poor black single parent households, usually a mother with multiple kids. This stems back from the last century where black people in Chicago were systemically forced into poor quality public housing like the notorious Cabrini Green and Robert Taylor projects. The housing authority enacted a policy that de facto forced fathers to move out in order for the family to maintain an affordable rent, which created the high rate of black single parent families that we still see today. This means the responsibility of both making money to support the family and also supervising the children falls solely on the mother a lot of the time, and a lot of them simply don't have the capacity to both work a job and effectively supervise their children. A lot of these kids also live in neighborhoods with severely underfunded schools and problems with gangs, so often not only are they not receiving parental supervision, they also live in an unsafe environment and lack opportunity. As a result, we have a ton of teens with no supervision and not much to lose descend on the loop and the beaches every spring once the temp goes above 70 degrees.