After increasing every year from 1997–98 to 2007–08, total variation in instruction expenditures per student was lower among public school districts in 2008–09 than in 2007–08.
A number of methods can be used to measure the variation between districts and states in the amount that school districts spend per student on instruction. The variation in instruction expenditures per student over time may reflect differences across school districts in the amount of services or goods purchased, such as the number of classroom teachers hired. These changes may, in part, reflect various state finance litigation, school finance reform efforts, and changes in the composition of student enrollment. Further, some of the variation in expenditures per pupil may be due to cost differences across states and districts within states. Changes in cost differences across and within states may also affect the changes in the variation over time.
This indicator uses the Theil coefficient to measure the variation in the instruction expenditures per student in unified public school districts for prekindergarten through grade 12. The Theil coefficient provides a national measure of differences in instruction expenditures per student that can be decomposed into separate components to measure school district-level variations both between and within states. The between-state and within-state components indicate whether the national variation in instruction expenditures per student is primarily due to differences in expenditures between states or within states. Similarly, the trends in the two components indicate whether the change over time in the national variation of instruction expenditures per student is primarily due to changes between states or changes within states. The Theil coefficient can range from zero, indicating no variation, to a maximum possible value of 1.0. The value of the Theil coefficient remains unchanged if expenditures in all districts are increased by the same percentage; it would therefore not be necessary to adjust instruction expenditures for inflation at the national level.
Across U.S. districts, the total variation in instruction expenditures per student decreased between school years 1989–90 and 1997–98, then increased between 1997–98 and 2007–08 (see table A-21-1). The total variation in instruction expenditures per student was greater in 2007–08 than it was in the early 1990s. Total variation was lower in 2008–09 than in 2007–08, but was still higher than in any year from 1989–90 through 2005–06. Both the between-state and within-state variations in instruction expenditures per student decreased between 1989–90 and 1997–98, and increased between 1997–98 and 2007–08. Like the total variation, both between-state and within-state variations were lower in 2008–09 than in 2007–08.
Between 1989–90 and 2008–09, differences between states accounted for a greater proportion of the variation in instruction expenditures per student among public school districts than did differences within states. The percentage of the total variation due to between-state differences increased from 72 percent in 1989–90 to 79 percent in 2008–09, while the percentage of the total variation due to within-state differences decreased from 28 to 21 percent.
For more information on the variation in expenditures per student, the Theil coefficient, and the classifications of expenditures for elementary and secondary education, see Appendix C – Finance . This indicator only includes unified public elementary and secondary districts. Unified districts serve both elementary and secondary grades. The Theil coefficient was calculated for unified districts only in order to limit any variations in expenditures per pupil due to the grade levels of the school districts or due to districts serving only students in special programs. In 2008–09, approximately 92 percent of all public elementary and secondary school students were enrolled in unified school districts. For more information on the Common Core of Data, see Appendix B – Guide to Sources.
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