[Excerpt] In general, the goal of disability insurance is to replace a portion of a worker’s income should illness or disability prevent him or her from working. Individuals may receive disability benefits from either federal or state governments, or from private insurers. This report presents information on two components of federal disability benefits, those provided through the Social Security Disability Insurance (SSDI) and the Supplemental Security Income (SSI) programs. The SSDI program is an insurance program that provides benefits to individuals who have paid into the system and meet certain minimum work requirements. In contrast, the SSI program is a means-tested program that does not have work or contribution requirements, but restricts benefits to those who meet asset and resource limitations.