I think there is some definition fuzziness here. We started with "percentage of the population ... not able to contribute productive work", this mutated into "surplus population" which is not the same as "people with disabilities"?
A resonable (economic) definition of "disabled" is "not able to contribute productive work"...
Do you have in mind what Tyler Cowen calls ZMP (zero marginal productivity) workers?
A resonable (economic) definition of "disabled" is "not able to contribute productive work"...
Agreed, but my impression is that SSI is targeted at medical disabilities- "I used to be a manual laborer but I now have persistent back pain" instead of "I used to be a manual laborer but now I'm structurally unemployed." The system as is encourages the medicalization of economic issues- and in particular of exaggerating the medical impact of issues rather than ameliorating them.
A post from Gregory Cochran's and Henry Harpending's excellent blog West Hunter.
The commenter Ron Pavellas adds:
The Wasserman Test.