Historically, the average difference between the actual values and the projections of current-fund expenditures of public degree-granting institutions has been about 2 percent for projections that are 2 or 3 years out from the year of the last actual data. Projections for years that are further out from the last year with actual data tend to be less accurate. The average difference between the actual values and projections 7 or more years out from the last year with actual data generally has been about 4 to 5 percent for both current-fund expenditures of public 4-year institutions and current-fund expenditures of public 2-year institutions.
Long-term projections that are economically based, such as projections of expenditures, are generally less accurate than long-term demographic projections, such as projections of elementary and secondary enrollment. NCES projections of current-fund expenditures of public degree-granting institutions produced over the last 9 years generally have been less accurate than recent NCES projections of public elementary and secondary enrollment. They have been more accurate than projections of teacher salaries. They have been similar in accuracy to projections of current expenditures in elementary and secondary schools. See appendix A for further discussion of the accuracy of recent projections of expenditures of public degree-granting institutions, and see table A2 in appendix A for the mean absolute percentage errors (MAPEs) of these projections.
