As of 2018, fluent speakers in Jeju Island were all over seventy years of age, while passive competence was found in some people in their forties and fifties. Younger Islanders speak Korean with Jeju substrate influence found in residual elements of the Jeju verbal paradigm and in select vocabulary such as kinship terms. The language is more vigorous in Osaka, where there may be fluent speakers born as late as the 1960s. Since 2010, UNESCO has classified Jeju as a critically endangered language, defined as one whose "youngest speakers are grandparents and older... speak the language partially and infrequently."