“…Current definitions of disability are based on clinical taxonomies of medical impairments, rather than on scales of functional ability or of economic need (Nagi, 1977;Stone, 1978a). Research on health program evaluation has led to the development of functionally-based health indices, which might fruitfully be applied to disability programs as administrative tools rather than as evaluative tools (Fanshel and Bush, 1970;Patrick et al, 1973;Lipscomb, 1978). If disability determinations could be based on real tests of performance or functional capabilities, the distortion of translating medical impairments into income losses could be reduced.…”