 Note that Roemer’s definition is a partition of \(N\) into two mutually exclusive and jointly exhaustive subset groups. As such, it precludes the possibility of a third group with neutral exploitation status.  This feature might not be particularly odd if we think that society divides rather crudely into two groups: exploiting capitalists and exploited workers. However, Roemer himself allows for and theorises the existence of more than two classes. One explanation for this feature of the definition is that it simply arises from Roemer’s coalitional approach.