It is difficult to ascertain the number and characteristics of persons experiencing homelessness due to the transient nature of the population, although attempts to collect information about homeless individuals have been made in recent decades. Beginning in the mid-1990s, for example, the Department of Housing and Urban Development (HUD) required its grant recipients to provide information about the homeless clients they served. In addition, comprehensive attempts to count homeless individuals were made in both the 1980s and 1990s, first via Census data and then through a national collaborative survey called the National Survey of Homeless Assistance Providers and Clients. However, no systematic method for collecting information about homeless persons has existed until recent years. In response to a directive from Congress in 1998, HUD began in 2001 to develop a system to collect information about homeless individuals; the processes of data collection, organization, and storage systems, which take place at the local level, have been termed Homeless Management Information Systems (HMIS). In July 2009, HUD released results of its fourth analysis of HMIS data—the fourth Annual Homeless Assessment Report (AHAR). This CRS report describes the development of HMIS, the results of the four AHARs, and previous attempts to count homeless individuals. Homeless Management Information Systems (HMIS) are databases established at the local level through which homeless service providers collect, organize, and store information about homeless clients who receive services. HUD is implementing the HMIS initiative through local "Continuums of Care" (CoCs), which acquire and process data from all participating local service providers. CoCs are local boards formed by communities—typically cities, counties, or combinations of both—made up of representatives from nonprofit service providers, advocacy groups, local government, and other interested organizations. Local boards identify the needs of homeless persons in their communities and try to ensure that they receive the appropriate mix of preventative assistance, emergency services, transitional housing, supportive services, and permanent housing. Local homeless services providers submit requests for funding to their local CoCs, which each in turn submit single consolidated applications to HUD. As of 2009, there were approximately 450 CoCs, including those in the territories. Two types of organizations are required to participate in HMIS: those that receive funding through the Housing Opportunities for Persons with AIDS (HOPWA) program and those that receive Homeless Assistance Grants. The HOPWA program, enacted in 1990 ( P.L. 101-625 ) provides housing and supportive services for persons living with HIV/AIDS. The Homeless Assistance Grants, enacted as part of the McKinney-Vento Homeless Assistance Act ( P.L. 100-77 ), consist of both formula grants, which are distributed through the Emergency Shelter Grants program, and competitive grants, which are available through the Shelter Plus Care program, Supportive Housing Program, and Section 8 Moderate Rehabilitation Assistance for Single Room Occupancy Dwellings program. Other service providers that serve homeless individuals and families but do not receive federal funds from these sources are also encouraged to participate in HMIS. Even prior to the congressional directive to implement HMIS (described in the next section of this report, " Development of the HMIS Network "), HUD began efforts to collect information about homeless clients served in the communities that receive HUD Homeless Assistance Grants. Beginning in the mid-1990s, about the time that the Continuum of Care system developed, HUD required applicants for Homeless Assistance Grants to include in their applications information about the number of persons receiving assistance and the type of assistance they received. Initially this was done in narrative form. However, by 2003, the grant application required CoC applicants to complete a housing activity chart that included a point-in-time count of homeless individuals and families receiving services, though HUD did not specify when this count should take place. The 2003 application also asked applicants to categorize subpopulations served, including the number of chronically homeless individuals, veterans, those with severe mental illnesses, those with HIV/AIDS, and victims of domestic violence. Some CoCs used database systems similar to HMIS to keep track of homeless individuals who were served; these predecessor systems are sometimes referred to as "legacy systems." The 2005 HUD point-in-time count of homeless persons marked the first time that HUD required all CoCs to conduct a count of both sheltered and unsheltered homeless individuals, and to do it at a particular time of year. HUD directed CoCs to conduct a one-night count during the last week of January of both clients who used homeless services and those who were on the street. HUD continues to require CoCs to conduct point-in-time counts every two years, though some CoCs choose to conduct counts every year. For example, in 2008, approximately 67% of CoCs voluntarily conducted counts. The most recent point-in-time count in which all CoCs participated occurred in January 2009. The results of CoC point-in-time counts are described later in this report, in the section " CoC Point-in-Time Estimates of Homeless Individuals ." HUD's ongoing attempts to collect information about homeless individuals were given greater direction beginning in 1998, when Congress instructed HUD to count homeless persons and gather data about both their characteristics and use of homeless assistance services. The FY1999 HUD spending bill ( P.L. 105-276 ) set aside up to 1% of the total appropriation for Homeless Assistance Grants for systems to collect information about those persons experiencing homelessness. Specifically, Congress directed HUD to produce an unduplicated count of homeless persons and to collect information about homeless individuals surveyed such as age, race, sex, disability status, health status, and income; the types of services that homeless clients received; and client outcomes such as length of stay in transitional housing, success in acquiring permanent housing, and employment status. Congress concluded that this information would allow HUD to better assess the quality of service programs supported with federal funds. Congress provided further direction to HUD in the HUD Appropriations Act for FY2001 ( P.L. 106-377 ). The law made Supportive Housing Program funds available for local CoCs to implement management information systems. Congress directed HUD to work with local jurisdictions to develop a system to collect data, and to be ready to analyze the data within three years of passage of the appropriations bill. Congress also requested that HUD provide Congress with a report on its findings containing an unduplicated count of homeless persons and a descriptive profile of the population. The FY2001 Appropriations Act once again allocated funds to pay for data collection, this time setting aside 1.5% of the $1.02 billion appropriation for Homeless Assistance Grants. Congress has continued to allocate funds for homeless data collection in spending bills from FY2002 to FY2009. In the time since Congress directed HUD to implement a system to count homeless persons and collect information about their characteristics, HUD has issued six annual reports to Congress updating its progress. In an initial report, dated August 2001, HUD stated that it would help CoCs collect homelessness data through four means: flexibly implementing the new Homeless Management Information System (HMIS) eligible activity under the Supportive Housing Program in the 2001 McKinney-Vento competition; initiating a comprehensive technical assistance program to help local jurisdictions collect unduplicated client-level data by 2004; developing an approach to obtaining meaningful data for an Annual Homeless Assessment Report from a nationally representative sample of jurisdictions; and analyzing the most viable approaches to obtaining homeless client-level reporting. Since issuing this 2001 report, HUD has initiated a number of activities to follow through on its pledge to assist CoCs. It specified that CoCs may use Supportive Housing Program funds for computer hardware, software, and personnel to manage and operate information systems, analyze HMIS data, and produce reports. HUD technical assistance teams hold training sessions for CoCs across the country, and HUD sponsors national conferences in which it provides sessions on a wide range of topics, including data entry, strategies for including data on domestic violence clients and chronically homeless individuals, and how to use HMIS to evaluate program performance and improve services to persons experiencing homelessness. HUD established a website—HMIS.Info—where information about HMIS implementation across the country can be disseminated. On July 30, 2004, HUD released its final notice on HMIS data and technical standards that local CoCs are expected to follow when they collect information about their homeless clients. The standards describe two levels of data collection—universal data, which homeless service providers must collect from all clients, and program-specific data, which programs that receive certain types of funding must collect but that other programs are encouraged to collect as well. All participants must report on universal data elements, which include name, date of birth, race, ethnicity, gender, veteran status, Social Security Number, prior residence, and disabling conditions. In general, all programs that receive funds under the McKinney-Vento Homeless Assistance Grants and HOPWA are required to provide program-specific data; this requirement is not new, as HUD already requires grantee organizations to provide this information in their Annual Progress Reports. Included in program-specific data elements are amount and sources of income, receipt of non-cash benefits, physical and developmental disabilities, HIV status, mental illness, substance abuse status, domestic violence status, services provided, and client outcomes. The HUD data standards were updated in 2009. Among the changes are a new universal data element regarding homeless status that is meant to distinguish those at risk of becoming homeless from those who meet HUD's current definition of homelessness. This category will capture those individuals and families being served through the new Homelessness Prevention and Rapid Re-Housing Program (HPRP).