From the Document: "The term 'retention' refers to the rate at which military personnel voluntarily choose to stay in the military after their obligated term of service has ended (as determined by their enlistment contract). Imbalances in the retention rate can cause problems within the military personnel system. A common retention concern is that too few people will stay in, thereby creating a shortage of experienced leaders, decreasing military efficiency, and lowering job satisfaction. This was a particular concern from 2004 to 2009, as the stress of major combat deployments to Iraq and Afghanistan raised concerns about the willingness of military personnel to continue serving. The opposite concern may also occur at times, particularly during force drawdowns: that too many people will stay in, thereby decreasing promotion opportunities and possibly requiring involuntarily separations to prevent the organization from becoming 'top heavy' with middle- and upper-level leaders or to comply with end-strength limitations. Each of these imbalances can also have a negative impact on recruiting by making the military a less-attractive career option."
CRS In Focus, IF11274
Congressional Research Service: https://crsreports.congress.gov/