Key points are not available for this paper at this time.
Richard J. Murnane, Judith D. Singer, John B. Willett, The Career Paths of Teachers: Implications for Teacher Supply and Methodological Lessons for Research, Educational Researcher, Vol. 17, No. 6 (Aug. - Sep., 1988), pp. 22-30
Murnane et al. (Mon,) studied this question.