Barbara Harff and Ted Gurr defined genocide as "the promotion and execution of policies by a state or its agents which result in the deaths of a substantial portion of a group ...[when] the victimized groups are defined primarily in terms of their communal characteristics, i.e., ethnicity, religion or nationality." Harff and Gurr also differentiate between genocides and politicides by the characteristics by which members of a group are identified by the state. In genocides, the victimized groups are defined primarily in terms of their communal characteristics, i.e., ethnicity, religion or nationality. In politicides the victim groups are defined primarily in terms of their hierarchical position or political opposition to the regime and dominant groups. Daniel D. Polsby and Don B. Kates, Jr. state that "... we follow Harff's distinction between genocides and 'pogroms,' which she describes as 'short-lived outbursts by mobs, which, although often condoned by authorities, rarely persist.' If the violence persists for long enough, however, Harff argues, the distinction between condonation and complicity collapses."