Because of the historic separation of western and eastern Ukraine under Polish and Russian spheres of influence, respectively, regional subpopulations have been seen as an important factor in Ukrainian politics. Arel and Wilson argue that the division on the all-important “Russian question” in Ukraine (relations with Russia and with the Russian-speaking minority) is increasingly regional: east and south versus the center and west. Hesli calculated the level of russification and industrialization in the various regions of Ukraine and concluded that both, together with geographic location, although interrelated, have their own bearing on variation in public opinion. Markus, however, has argued that despite economic, political and ethnic differences among Ukraine's regions, these differences pose less of a threat to reform than has sometimes been suggested. She further points out that speculation that the Donbass wants to unite with Russia “stems more from Russian claims to the area than from genuine indigenous sentiment.” Miller and colleagues, on the other hand, dispute the notion of regional differences independent of the socio-demographic characteristics of the local populations, challenging the conventional wisdom that there are regional political cultures that supersede any underlying demographic differences. They argue that national, political, economic and class identities represent the important cleavages in post-communist societies. The regional divide in Ukraine is thus not a foregone conclusion but a factor that bears closer examination.