The Marine Corps' Performance Evaluation System (PES) rates Marines against their peers through marks populated onto “master brief sheets” used by promotion boards. The marks often tell a story—a Marine's performance is either below average, average, or above average when compared with others. The process eliminates the need for dissecting individual reports to discover what a Marine's overall performance value is, since raters rank Marines in order from best to worst.
As efficient as this system is, it has one critical shortcoming: PES is entirely reliant on the opinions of senior-ranking officers. How effective is this Marine at leading? How will this Marine lead others as a captain? Is this Marine prepared to assume the additional responsibilities associated with being a gunnery sergeant of Marines? The answers to these questions are often found in the reporting senior (RS) and reviewing official (RO) comment sections of an individual Marine's fitness report.