This article identifies several mathematical and conceptual problems w
ith Massey and Denton's (1988a) Relative Concentration index (RCO). Ma
ssey and Denton Proposed this index to measure the spatial concentrati
on of minority groups, a dimension of segregation they identify as rel
evant to their ''hypersegregation'' hypothesis. This index has also in
fluenced segregation research and has been replicated in U.S. Census B
ureau analyses by Harrison and Weinberg (1992).