Data from the Monitoring the Future project, a study of high school seniors (and since 1991, eighth and tenth graders) are used to define six recruitment periods in America's all-volunteer military force, characterized by variations in entry-level pay, recruiting resources, educational benefit programs available, the recruiting environment, and recruit quality. Propensity to enlist is shown to drop between the eighth and the twelfth grades, and between 1991 and 1997 at each grade level studied. Propensity is also shown to have varied between 1976 and 1997 by gender, race, and college plans