The portion of the nation's affordable housing supply that tends to serve the lowest income households is rental housing subsidized by the federal government, through the Department of Housing and Urban Development (HUD) and to a lesser extent, the Rural Development Division (RD) of the U.S. Department of Agriculture. Within HUD, the major programs are Public Housing, Multifamily Subsidized Housing, Project-Based Section 8, and the Section 8 voucher program. Within, RD the Section 515 Rural Rental Housing Program is the major resource available in rural areas for low income households. In recent years, Congress established the Low Income Housing Tax Credit program (LIHTC) as the major new affordable housing production program. A substantial portion of the projects and units within these programs are at risk of loss from the affordable housing supply, either because the units may be lost or, more commonly, the private owners of these units seek to convert their buildings to market rate rents. From its inception, HPP has specialized in developing legal and advocacy strategies, working in conjunction with residents and community organizations, to retain these badly needed resources within the affordable housing programs.