It's based on past earned wages.
SSI is a set amount determined by the state legislatures. But such folks can get Medicaid, which has part state and part federal funding, and the amount varies from state to state on eligiblity.
I'm fairly well-versed on SS, SSDI and Medicare; they are federal programs. Medicaid and SSI are not part of the lives of people I know unless they are considered to be indigent or 'catastrophically medically indigent' thus eligible to SSI and Medicaid.
SSI supplements both SS and SSDI is the person is eligible. And it's been a hell of a month for me here, also I haven't been involved in hearings for anyone for some years. Perhaps things have changed.
I onced lived in a redstate with traditional Medicaid and since I've moved many years ago, they have refused the expansion. Where I live we have the expansion for those eligible for Medicaid. The rest remains the same.
My dealings personally have been with the federal programs, except for those people I know who do qualify for Medicaid under the 'catastrophic, etc.' label. With their conditions, it would not matter how much money is in an account for them federally, the condition devours all of that and they are indigent and cannot live without the additional funding.
As far as their getting SSI, they do not as they are being cared for with services under Medicaid and have no use for cash to live on. I think you know what I am talking about.
See you later, jwirr.