New report from Brookings by Matthew F. Cancian and Michael W. Klein:

In this paper, we show that the quality of officers in the Marines, as measured by scores on the General Classification Test (GCT), a test that all officers take, has steadily and significantly declined since 1980.

I would like to know if the result is robust across all branches of service.

This paper analyzed the quality of the officers of one branch of the military, the Marine Corps, and found a relevant and steady decline in intelligence, as measured by GCT scores, since 1980. This decline was closely associated with an expansion of the pool of young college graduates during the same time period, which potentially diminished the overall intellectual quality of that pool.