Trends in recruiting 1975–2001 showing total numbers of enlisted recruits in all branches of US armed forces in light blue and percentage of recruiting goals met in dark blue. Percentage of recruits with at least a high school diploma is shown in gold, percentage with an above average AFQT in orange, and the percentage called "high quality", with both a diploma and above-average AFQT score, is in purple.
Each service has a uniformed head who is considered the highest-ranking officer within their respective service, with the exception of the chairman and vice chairman of the Joint Chiefs of Staff, and the chief of the National Guard Bureau. They are responsible for ensuring personnel readiness, policy, planning and training and equipping their respective military services for the combatant commanders to utilize. They also serve as senior military advisors to the President, the Secretary of Defense, their respective service secretaries, as well as other councils they may be called to serve on. They are as follows:
Mathematics Knowledge tests the ability to solve problems by applying knowledge of mathematical concepts and applications. The problems focus on concepts and algorithms, and involve number theory, numeration, algebraic operations and equations, geometry, measurement and probability. Mathematics Knowledge is one factor that characterizes mathematics comprehension; it also assesses logical thinking.