In 1975, DOD implemented the Reserve Components Common Personnel Data System (RCCPDS) to collect information on current and past members of the six reserve components—Army National Guard, Air National Guard, Army Reserve, Navy Reserve, Marine Corps Reserve, and Air Force Reserve. This information included data on reservists’ personal characteristics, such as name, Social Security number, date of birth, gender, home address, and education, as well as data on their military characteristics, such as service, reserve component, prior service status, and date of initial entry into the reserve forces. According to the director of DMDC, the services send daily, weekly, and monthly updated data submissions to DMDC in accordance with applicable guidance. After the first Gulf War, in a May 15, 1991, memorandum, DOD identified 16 recommendations requiring action by many offices within DOD regarding Desert Storm personnel data issues. For example, the memorandum said that DOD should consistently report on who participated in the operations and cites examples of key terms, such as in theater, that were being interpreted differently by DMDC, the Office of the Secretary of Defense, and the services. In December 1991, DOD reported on how DMDC provided information about operations Desert Shield and Desert Storm. This report cited areas for improvement. For example, the report indicated that DMDC created makeshift procedures to establish and maintain the new data sources and to accommodate varied data requests. The report cited that these procedures sometimes resulted in inconsistent or incomplete data being provided in response to a request. On May 2, 2001, DOD updated guidance to the military services, among others, to maintain a centralized database of active duty personnel. In this guidance, DOD requires the services to report personnel information about all active duty military servicemembers as well as reservists who are ordered to active duty. While this instruction called for the services to report information about servicemembers on active duty in support of a contingency, the requirements for reporting contingency data were not specific. On October 4, 2001, the Under Secretary of Defense, Personnel and Readiness (USD (P&R)), issued a memorandum that required the services to report personnel information to DMDC on all active and reserve component personnel mobilized or deployed in support of GWOT, in accordance with DOD guidance. The purpose of GWOT data was, among other things, to establish eligibility for benefits and entitlements as a result of participation in the named contingencies. The information is critical because it provides a historical database with which to assess the impact of policies and processes, events, and exposures on the health of deployed reserve component servicemembers. DMDC was tasked with providing reporting guidance to the services for these data submissions. DMDC sent this guidance to the services on October 12, 2001. DMDC is a civilian-led agency with a mission to deliver timely and quality support to its customers, and to ensure that data received from different sources are consistent, accurate, and appropriate when used to respond to inquiries. DMDC reports to the Deputy Under Secretary of Defense for Program Integration, who is in the Office of the USD (P&R) (see fig. 1). In February 2002, USD (P&R) reminded the services in another memorandum of its earlier requirement for reporting personnel data to DMDC and informed the services that they had 2 weeks to provide plans to DMDC on how they were going to correct any personnel data reporting problems. On August 6, 2004, DOD updated prior guidance regarding RCCPDS to include an enclosure that set out specific requirements for the services to report personnel information for all reserve component servicemembers supporting a named contingency, unlike previous guidance. The purpose of the new enclosure was to ensure more accurate reporting on a named contingency, such as GWOT missions, as well as to establish eligibility for benefits and entitlements, and to develop a registry of participants for tracking in support of research and evaluation of DOD programs and policies. According to DOD officials, the services, in general, were still reporting data according to previous guidance for a few years after the new guidance was issued. In August 2004, DMDC began operation of its CTS database to address DOD’s reporting requirements, including those in the new enclosure (that is, enclosure 11). The CTS database is DOD’s repository for collecting activation, mobilization, and deployment data for reservists who have served and continue to serve in support of GWOT. The CTS database contains both an activation file, which contains mobilization data, and a deployment file. Both files are updated monthly by service submissions and cover GWOT from September 11, 2001, to the present. The purpose of the activation file is to account for and provide medical and educational benefits for all reservists called to active duty in support of GWOT contingencies, and it allows DOD to provide data on the number of reservists who have been mobilized in support of GWOT. The purpose of the CTS deployment file is to account for a deployed servicemember’s deployment date and location during each deployment event in support of deployment health surveillance and DOD guidance. The database is also used to track and report the number of reservists who have been deployed in support of GWOT since September 11, 2001. Our analysis of DOD data indicates that more than 531,000 reservists have been mobilized in support of GWOT and more than 378,000 reservists, or about 71 percent of the number mobilized, have been deployed in support of GWOT through June 30, 2006 (see fig. 2). The Army National Guard deployed the greatest number of reservists in support of GWOT from September 2001 through June 30, 2006, and, of those, the majority were deployed once. The data also indicate that the vast majority of reservists who deployed in support of GWOT were U.S. citizens, White, and male. Further, the data indicate that most of the reservists spent 1 year or less deployed. DOD guidance requires the services to report timely, accurate, and complete activation, mobilization, and deployment data. DOD guidance also requires DMDC to collect and maintain mobilization and deployment data from the services about the reservists. DOD is required by policy to report personnel data about reservists, such as service, service component, reserve component category, race, ethnicity, gender, citizenship status, occupation, unit, and volunteer status regarding a current mobilization. In addition, DOD is required by policy to capture deployment information such as the location a reservist is deployed to and the dates the reservist was deployed to that location. Our analysis of DOD data indicates that more than 531,000 reservists have been mobilized in support of GWOT and more than 378,000 reservists, or 71 percent of the number mobilized, have been deployed in support of GWOT through June 30, 2006 (see fig. 2). The number of mobilizations and deployments peaked in fiscal year 2003 with about 206,000 reservists mobilized and about 127,000 reservists deployed (see figs. 3 and 4). Since fiscal year 2003, the total number of mobilizations has declined, while the number of deployments remained stable through fiscal year 2005. The Army National Guard has mobilized and deployed the greatest number of reservists—more than 230,000 mobilized and more than 163,000 deployed. The Navy Reserve had the least number of reservists mobilized—with about 29,000—while the Marine Corps Reserve had the fewest number deployed with about 19,000 reservists (see fig. 2). The percentage of the total reservists mobilized or deployed varies across the fiscal years (see figs. 3 and 4). For example, looking at the percentage of mobilizations by component each year, Navy Reserve, Air Force Reserve, and Air National Guard mobilizations occurred early in GWOT and have generally declined over time. Conversely, the percentage of Army National Guard and Army Reserve mobilizations has generally increased over time. The greatest number of Army National Guard deployments—more than 60,000— occurred in fiscal year 2005 (see table 5 totals in app. II), while also in fiscal year 2005, the Army National Guard represented the largest deploying component, with 52 percent of deployments belonging to it (see fig. 4). Although reservists usually deployed only once, some experienced multiple deployments (see fig. 5). For example, compared to the other reserve components, the Air National Guard and the Air Force Reserve had nearly half of their reservists deploying two and three or more times, but they tend to have shorter deployment cycles according to the Air Expeditionary Force cycle. Under this cycle, reservists deploy for about 120 days in a 20-month cycle. However, servicemembers assigned to stressed specialties deploy for longer periods of time and in greater frequency. At the unit level, some deployment rules have been modified to increase volunteerism or to add stability to key missions. The Army National Guard and the Marine Corps Reserve had the lowest percentage of reservists deploying two and three or more times, but they tend to have longer deployment cycles. In general, DOD policy stipulates that Army units spend 1 year “boots on the ground” in theater. This policy also states that Marine Corps units below the regimental or group level deploy for 7 months while regimental and group headquarters units and above deploy for 12 months. This policy also states that the Chief of Naval Operations’ goal is for servicemembers to have a 6-month deployment with 12 months in a nondeployed status. Our analysis of DOD data indicates that across the services, the majority of reservists have been deployed once, and of those deployed in support of GWOT, most—about 307,000 reservists, or 81 percent—have spent a year or less deployed.