 While the rise of Ava ensured the continued spread of Burman ethnicity in post-Pagan Upper Burma, the similar emergence of non-Burmese speaking kingdoms elsewhere helped develop ethnic consciousness closely tied to respective ruling classes in Lower Burma, Shan states and Arakan.For example, according to Lieberman and Aung-Thwin, "the very notion of Mons as a coherent ethnicity may have emerged only in the 14th and 15th centuries after the collapse of Upper Burman hegemony".Pagan's society was highly stratified among different social classes.