When he took office as California Governor, the State had a great system of mental health hospitals. Ronnie wanted to save money by closing them and sending the patients to live in the community where there would be walk in clinics. Plan failed and the homeless population skyrocketed. Which meant that the citizens needed more police and jails to control the miscreants.
ACF, and just about everybody else, seems to cite the National Foster Youth Institute, https://nfyi.org/issues/homelessness/ but I can't find how they came up with that number.
Also kids that don't get adopted disproportionately have special needs that require medicines and other medical care and we don't have universal health care.