Changes in the labor market in the last 20 years are evaluated in order to examine the impact of teacher unionization, the extent of teacher mobility and responsiveness to wage differentials, and the projected demand for teachers from 1980 to 2000. Using cross-section wage regressions and wage change regressions, the study shows that the union-nonunion wage differential has increased rapidly in the 1970s. Regression techniques also reveal that teachers are at least as responsive to wage differentials as other workers, although differentials between teaching and alternative jobs affect educators more than differentials between teaching jobs. The study predicts a modest decline in teacher demand into the mid-to-late 1980s, followed by a modest gain. Over a period of time, demand is found to be fairly insensitive to real wage trends. (Author/WD)