For 90 percent of L.A. County's homeless population, public costs average $710 a month - mostly covering health services, public assistance, and the justice system. For the other 10 percent, it's $8,083. For those who are off the streets and in supportive housing programs, it's $605. The numbers are part of a study by L.A.'s Economic Roundtable that suggests how much of a lifeline those housing programs can be, both for the participants involved and for government budgets. But getting back to that 10 percent of the homeless population: What makes their costs so much higher? There are 10 characteristics that are at least 50 percent more frequent in this group:

1. Inpatient in a county hospital in the past 2 years: 852 percent more frequent
2. Incarcerated in jail mental health facility in past 5 years: 343 percent more frequent
3. Living with HIV/AIDS: 319 percent more frequent
4. Incarcerated in jail medical facility in the past 5 years: 229 percent more frequent
5. Visitor to county emergency room in past 2 years: 216 percent more frequent
6. Mental illness: 139 percent more frequent
7. Substance abuse problem: 90 percent more frequent
8. Disability: 70 percent more frequent
9. Probation record in past 3 years: 70 percent more frequent
10. Any type of jail in the past 5 years: 50 percent more frequent

None of this is likely to be a huge surprise among those who work closely with homeless people. But among those who don't, it may be a helpful explanation on why government assistance at this level is so necessary - the same government assistance, by the way, that's being slashed to smithereens.