RAND has developed the Readiness Enhancement Model, a personnel inventory projection model for the Army's Reserve Components. The model supported research carried out under the Arroyo Center's Reserve Component personnel readiness project. Project findings are described fully in Bruce Orvis et al., Ensuring Personnel Readiness in the Army Reserve Components, MR-659-A, 1996. The reader who intends to employ the model should find this report useful. Readers who do not plan to employ the model should also find portions of the report useful as a vehicle for understanding the inventory projection environment within which the model operates. The project was designed to examine the true extent of cross-leveling during Operation Desert Shield/Storm, the reasons for it, the likelihood of serious personnel shortfalls in future deployments, and, based on these findings, the types of policies that could enhance the Reserve Components' readiness to deal with future contingencies. The model described in this report supported research designed to estimate how increased use of prior service experience and reduced Reserve Component attrition and job turbulence would affect job qualification rates and annual requirements for recruiting and training.