As the average ages of Army weapon systems increase, it has been assumed that this is leading to increasing maintenance costs. However, it has proved difficult to quantitatively "validate" and estimate the actual effect of equipment age on costs. In particular, it has been noted that increases in costs may have been "hidden" by how Army budgets are structured or mitigated by adaptations in part-ordering practices that are not reflected in spending and budgets. This study examines the relationship between equipment age and spare part costs for M1 Abrams tanks through the use of part requisition data. The authors also examine the issue of adaptive practices by comparing actual part expenditures to an exchange price-based valuation of part demands. This work is closely related to a companion study on the effects of equipment age on mission critical failures, a key component of equipment readiness.

"Prepared for the United States Army"--T.p.

Introduction -- Mitigating factors in studies of the effects of equipment age on maintenance costs -- Analysis of unit turn-in behavior -- Analysis of the effects of equipment age on spare part costs -- Implications and recommendations -- Appendix A: summary of data characteristics -- Appendix B: pre-SSF turn-in credit determination -- Appendix C: expensive items requested and turned in to produce negative actual expenditures -- Appendix D: additional statistical information on regression analyses.