 North America exhibits several varieties of English. They can be grouped according to ethnic parameters in which we would define dialects, like African American English or American Indian English, the English spoken by the indigenous inhabitants of North America. Phonologically, it seems reasonable to look at recent sound shifts as a defining criterion in the study of variations. For instance, the low back merger is a phonemic shift where two low back barrels merge. This sound shift is complete in many regions of North America, including the western United States, some of New England and most of Canada. The dialectal variety of the New York City diaspora and other regions, by contrast, can be recognized by its distinctive lack of this low back merger. Additionally, this variety exhibits a pronunciation split of the short R into two separate sounds. The diphthongization and upgliding of the short front vowels is a defining sound shift that creates the regionally distinct southern roll present in the southern United States. The northern city's vowel shift is a major sound shift that involves the movement of six vowels. This shift is currently in progress in the region near the Great Lakes. Canadian English is an under-described variety of English whose regional dialects have just recently been defined in Le Boeuf's Atlas of North American English. It exhibits a number of robust phonological features, such as Canadian raising and the Canadian shift.