and less rounded than Canadian . In Pittsburgh, where cot and caught are merged to a back rounded vowel, the mouth vowel is traditionally a monophthong that fills the low central space, thus preventing from retracting. Among younger speakers, however, begins to move backward as the monophthongization of declines. Durian (2008), via instrumental analysis, found evidence of the Canadian Shift in the vowel systems of men born circa 1965 and later in Columbus, Ohio, a city located within the U.S. Midland. is undergoing fronting without lowering, while still remaining distinct from the space occupied by . At the same time, historical (the vowel in "lot") is merged with the class. This allows a "free space" for the retraction of , a possibility also suggested for Western U.S. dialects being potentially capable of showing the Canadian Shift by Boberg (2005). In Columbus, the Canadian Shift closely resembles the version found by Boberg (2005) in Montreal, where and are either merged or "close," shows retraction of the nuclei (as well as "rising diphthong" behavior—i.e., ingliding with a lower nucleus than the glide), and as well as show retraction of the nucleus. (However, the retraction of was not found among all speakers and is more mild among the speakers that do show it than the retraction of among those speakers. Also, the outcome of low back merger-like behavior is more like the California Shift outcome noted above than the rounded variant found in Canada.) See also California shift Canadian raising Northern Cities Vowel Shift North-Central American English Notes Canadian English Vowel shifts