Old-age, survivors, and disability insurance (OASDI) is the United States Social Security system. This system is targeted at retirees, surviving spouses and (in some cases) children, and handicapped individuals, providing them with monthly benefit payments. The program was initiated by the Social Security Act in 1935, and has been expanded since then. The OASDI program now comprises the largest portion of the federal budget. It is funded by taxes levied on employers, employees, and the self-employed.