Factors affecting the projections
The projections of the number of elementary and secondary teachers are related to projected levels of enrollments and education revenue receipts from state sources per capita. For more details, see appendixes A. 0 and A.3.
Factors that were not considered
The projections do not take into account possible changes in the number of teachers due to the effects of government policies.
About pupil/teacher ratios
The overall elementary and secondary pupil/teacher ratio and pupil/teacher ratios for public and private schools were computed based on elementary and secondary enrollment and the number of classroom teachers by control of school.
About new teacher hires
A teacher is considered to be a new teacher hire for a certain control of school (public or private) for a given year if the teacher teaches in that control that year but had not taught in that control in the previous year. A teacher who moves from teaching in one control of school to the other control is considered a new teacher hire, but a teacher who moves from one school to another school in the same control is not considered a new teacher hire.
An analysis of projection errors from the past 21 editions of Projections of Education Statistics indicates that the mean absolute percentage errors (MAPEs) for projections of classroom teachers in public elementary and secondary schools were 0.8 percent for 1 years out, 1.4 percent for 2 years out, 2.8 percent for 5 years out, and 5.9 percent for 10 years out. For the 1-year-out prediction, this means that one would expect the projection to be within 0.8 percent of the actual value, on average. For more information on the MAPEs of different National Center for Education Statistics (NCES) projection series, see table A-2 in appendix A.