Vowel shifts
Like glide shortening, the vowel changes collectively known as the “Southern Shift” all either emerged during the last quarter of the 19th century or began to expand rapidly during that time. Although there is some debate about what exactly comprises the Southern Shift, the following processes have been included as part of it at one time or another:
(1) the fronting of the vowels in the GOOSE class to 
and in the FOOT class to 
,
(2) the fronting of the nucleus in the MOUTH class to [æo ~ εo],
(3) the fronting or fronting and lowering of the vowels in the GOAT class to 
,
(4) the lowering and retraction of vowels in the FACE class to 
, and
(5) in parts of the South, the lowering and retraction of the vowels in the FLEECE class to 
.
By the middle of the 20th century these developments had become defining characteristics of the SAmE vowel system in most areas of the South. Since World War II, the fronting of back vowels and of the nucleus of the diphthong in the MOUTH class has continued in urban SAmE, even surpassing the fronting in non-urban varieties, and has expanded to include the vowels in the STRUT class sometimes, which can be realized as [з] . The lowering and retraction of the front vowels, however, is receding in the largest metropolitan areas. For many urban Southerners born after 1970, the vowels in the FACE and FLEECE classes are as high as or higher than the vowels in the DRESS and KIT classes, and the tense member of the pair is often further to the front as well.
