According to Labov, Ash, and Boberg,the merger does not generally occur in the southern United States (with exceptions), along most of the American side of the Great Lakes region, or in the "Northeast Corridor" extended metropolitan region from Providence, Rhode Island to Baltimore. Areas that it occurs include:
[*]Canada
[*]Boston (see
Boston accent)
[*]Northeastern New England
[*]the Pittsburgh area (see
Pittsburghese)
[*]The Western United States
[*]Due to an apparent spread of the merger towards the center of the United States (from both the western and eastern states), portions of the Midwest also feature the merger:
[*]Illinois
[*]Indiana
[*]Iowa
[*]Minnesota
[*]Missouri
[*]Ohio
The distribution of the merger is complex, even without taking into account the mobility of the American population; there are pockets of speakers with the merger in areas that lack it, and vice versa. There are areas where the merger has only partially occurred, or is in a state of transition. For example, based on research directed by
William Labov (using telephone surveys), younger speakers in Kansas, Nebraska, and the Dakotas exhibit the merger while speakers older than 40 typically do not. The 2003 Harvard Dialect Survey, in which subjects did not necessarily grow up in the place they identified as the source of their dialect features, indicates that there are speakers of both merging and contrast-preserving accents throughout the country, though the basic isoglosses are almost identical to those revealed by Labov's 1996 telephone survey. Both surveys indicate that approximately 60% of American English speakers preserve the contrast, while approximately 40% make the merger, although in a more recent interview, Labov stated that "Half of this country has a merger of the word classes, cot, caught, don, dawn, hock, hawk."