The relative positions of the vowels in these figures show the changes ongoing in the Northern Cities Chain Shift. The raising of /æ/ and the lowering and backing of // are evident in Judy's and Rita's charts, since their relations are reversed as compared with the expected locations for Reference American (// is higher than /æ/ in RA), or for example, the relation seen between these vowels in Los Angeles Chicano speech (Figure , page ). While // is evidently backed for Jim (it is located as far back as the central low vowels and //), it is not apparently lowered in his phonetic vowel system, though /æ/ has raised to the same height as //. This is consistent with the view that the Northern Cities Chain Shift has progressed since 1970, when Jim was interviewed. /æ/-raising may be the first step in the chain shift,7.20 while the lowering and backing of // to [æ] and  is among the most recent changes. So if Jim's /æ/ is raised, but his // isn't lowered as much as // is lowered in Judy's and Rita's vowel systems, this is because Jim represents an intermediate stage of the chain shift.
The fronting of // is perhaps evident in the fact that for each of the three speakers, // lies to the front of /w/ and is distinct from it. // is the most low-front vowel in the system for all of them. That this is a drag chain shift is evident from the fact that /æ/ is fronted and raised a great distance away from //, leaving a large phonetic gap for // to move into.
The fronting of // proceeds gradually, from Jim, for whom // is well to the back of /r, w, , y/, to Rita, for whom // is quite close to /r, w/, to Judy, for whom // has become the lowest vowel in the system, and is almost indistinguishable (in terms of average nuclei in F1-F2 space) from /w/.
The approximation of // with the /-/ vowels, /, w, r/, in Judy's speech raises the question of merger: Will Chicago undergo the Low-Back Merger? It has not apparently done so yet, but the difference between // and // is quite small for Judy.
The lowering of // (which precedes //-lowering, discussed above) is evident by its relationship with /ow/, which is much higher than // for Judy and Jim, though not for Rita.
Thus each of the steps of the Northern Cities Chain Shift, as well as the fronting of the high back vowels, /uw, /, are evident in Figures -.
The fronting of the high back vowels, /uw, / is not evident for Jim, where these vowels are as far back as /ow, or/. But in both Judy and Rita's charts, /uw, / are well to the front of /ow, or/, again reflecting the progress of sound change in the intervening 20 years.