A technique for measuring the effect of economic base on opportunity for blacks.

An assessment of the occupational opportunities for selected groups of in-migrants (i.e., Negroes) requires a technique which controls for effects of both national and local employment patterns. We suggest a measure based upon the location quotient and referred to as the "differential opportunity ratio" as a method which provides the necessary controls. It is applicable in the comparative studies of cities and in analyses of other population groups for which data are available.